=head1 NAME
-perldelta - what's new for perl v5.6 (as of v5.005_64)
+perldelta - what's new for perl v5.6.0
=head1 DESCRIPTION
-This is an unsupported alpha release, meant for intrepid Perl
-developers only. The included sources may not even build correctly on
-some platforms. Subscribing to perl5-porters is the best way to
-monitor and contribute to the progress of development releases (see
-http://www.hut.fi/~jhi/perl5-porters.html for info).
-
This document describes differences between the 5.005 release and this one.
-=head1 Incompatible Changes
+=head1 Core Enhancements
-=head2 Perl Source Incompatibilities
+=head2 Interpreter cloning, threads, and concurrency
-Beware that any new warnings that have been added or old ones
-that have been enhanced are B<not> considered incompatible changes.
+Perl 5.005_63 introduces the beginnings of support for running multiple
+interpreters concurrently in different threads. In conjunction with
+the perl_clone() API call, which can be used to selectively duplicate
+the state of any given interpreter, it is possible to compile a
+piece of code once in an interpreter, clone that interpreter
+one or more times, and run all the resulting interpreters in distinct
+threads.
-Since all new warnings must be explicitly requested via the C<-w>
-switch or the C<warnings> pragma, it is ultimately the programmer's
-responsibility to ensure that warnings are enabled judiciously.
+On the Windows platform, this feature is used to emulate fork() at the
+interpreter level. See L<perlfork> for details about that.
-=over 4
+This feature is still in evolution. It is eventually meant to be used
+to selectively clone a subroutine and data reachable from that
+subroutine in a separate interpreter and run the cloned subroutine
+in a separate thread. Since there is no shared data between the
+interpreters, little or no locking will be needed (unless parts of
+the symbol table are explicitly shared). This is obviously intended
+to be an easy-to-use replacement for the existing threads support.
-=item CHECK is a new keyword
+Support for cloning interpreters and interpreter concurrency can be
+enabled using the -Dusethreads Configure option (see win32/Makefile for
+how to enable it on Windows.) The resulting perl executable will be
+functionally identical to one that was built with -Dmultiplicity, but
+the perl_clone() API call will only be available in the former.
-In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
-subroutines named C<CHECK> are now special. These are queued up during
-compilation and behave similar to END blocks, except they are called at
-the end of compilation rather than at the end of execution. They cannot
-be called directly.
+-Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn
+enables Perl source code changes that provide a clear separation between
+the op tree and the data it operates with. The former is immutable, and
+can therefore be shared between an interpreter and all of its clones,
+while the latter is considered local to each interpreter, and is therefore
+copied for each clone.
-=item Treatment of list slices of undef has changed
+Note that building Perl with the -Dusemultiplicity Configure option
+is adequate if you wish to run multiple B<independent> interpreters
+concurrently in different threads. -Dusethreads only provides the
+additional functionality of the perl_clone() API call and other
+support for running B<cloned> interpreters concurrently.
-When taking a slice of a literal list (as opposed to a slice of
-an array or hash), Perl used to return an empty list if the
-result happened to be composed of all undef values.
+ NOTE: This is an experimental feature. Implementation details are
+ subject to change.
-The new behavior is to produce an empty list if (and only if)
-the original list was empty. Consider the following example:
+=head2 Lexically scoped warning categories
- @a = (1,undef,undef,2)[2,1,2];
+You can now control the granularity of warnings emitted by perl at a finer
+level using the C<use warnings> pragma. L<warnings> and L<perllexwarn>
+have copious documentation on this feature.
-The old behavior would have resulted in @a having no elements.
-The new behavior ensures it has three undefined elements.
+=head2 Unicode and UTF-8 support
-Note in particular that the behavior of slices of the following
-cases remains unchanged:
+Perl now uses UTF-8 as its internal representation for character
+strings. The C<utf8> and C<bytes> pragmas are used to control this support
+in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
+more information.
- @a = ()[1,2];
- @a = (getpwent)[7,0];
- @a = (anything_returning_empty_list())[2,1,2];
- @a = @b[2,1,2];
- @a = @c{'a','b','c'};
+This feature is expected to evolve quickly to support some form of I/O
+disciplines that can be used to specify the kind of input and output data
+(bytes or characters). Until that happens, additional modules from CPAN
+will be needed to complete the toolkit for dealing with Unicode.
-See L<perldata>.
+ NOTE: This should be considered an experimental feature. Implementation
+ details are subject to change.
+
+=head2 Support for interpolating named characters
+
+The new C<\N> escape interpolates named characters within strings.
+For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string
+with a unicode smiley face at the end.
+
+=head2 "our" declarations
+
+An "our" declaration introduces a value that can be best understood
+as a lexically scoped symbolic alias to a global variable in the
+package that was current where the variable was declared. This is
+mostly useful as an alternative to the C<vars> pragma, but also provides
+the opportunity to introduce typing and other attributes for such
+variables. See L<perlfunc/our>.
+
+=head2 Support for strings represented as a vector of ordinals
+
+Literals of the form C<v1.2.3.4> are now parsed as a string composed
+of characters with the specified ordinals. This is an alternative, more
+readable way to construct (possibly unicode) strings instead of
+interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
+C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
+parsed the same as C<v1.2.3>.
+
+Strings written in this form are also useful to represent version "numbers".
+It is easy to compare such version "numbers" (which are really just plain
+strings) using any of the usual string comparison operators C<eq>, C<ne>,
+C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
+C<&>, etc.
+
+In conjunction with the new C<$^V> magic variable (which contains
+the perl version as a string), such literals can be used as a readable way
+to check if you're running a particular version of Perl:
+
+ # this will parse in older versions of Perl also
+ if ($^V and $^V gt v5.6.0) {
+ # new features supported
+ }
+
+C<require> and C<use> also have some special magic to support such literals.
+They will be interpreted as a version rather than as a module name:
+
+ require v5.6.0; # croak if $^V lt v5.6.0
+ use v5.6.0; # same, but croaks at compile-time
+
+Alternatively, the C<v> may be omitted if there is more than one dot:
+
+ require 5.6.0;
+ use 5.6.0;
+
+Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
+to print ordinals of characters in arbitrary strings:
+
+ printf "v%vd", $^V; # prints current version, such as "v5.5.650"
+ printf "%*vX", ":", $addr; # formats IPv6 address
+ printf "%*vb", " ", $bits; # displays bitstring
+
+See L<perldata/"Scalar value constructors"> for additional information.
-=head2 Perl's version numbering has changed
+=head2 Improved Perl version numbering system
-Beginning with Perl version 5.6, the version number convention has been
+Beginning with Perl version 5.6.0, the version number convention has been
changed to a "dotted integer" scheme that is more commonly found in open
source projects.
Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
-The next development series following v5.6 will be numbered v5.7.x,
+The next development series following v5.6.0 will be numbered v5.7.x,
beginning with v5.7.0, and the next major production release following
-v5.6 will be v5.8.
+v5.6.0 will be v5.8.0.
The English module now sets $PERL_VERSION to $^V (a string value) rather
than C<$]> (a numeric value). (This is a potential incompatibility.
To cope with the new versioning system's use of at least three significant
digits for each version component, the method used for incrementing the
subversion number has also changed slightly. We assume that versions older
-than v5.6 have been incrementing the subversion component in multiples of
+than v5.6.0 have been incrementing the subversion component in multiples of
10. Versions after v5.6.0 will increment them by 1. Thus, using the new
-notation, 5.005_03 is the same as v5.5.30, and the first maintenance
-version following v5.6.0 will be v5.6.1, which amounts to a floating point
-value of 5.006_001).
+notation, 5.005_03 is the "same" as v5.5.30, and the first maintenance
+version following v5.6.0 will be v5.6.1 (which should be read as being
+equivalent to a floating point value of 5.006_001 in the older format,
+stored in C<$]>).
-=item Literals of the form C<1.2.3> parse differently
+=head2 New syntax for declaring subroutine attributes
-Previously, numeric literals with more than one dot in them were
-interpreted as a floating point number concatenated with one or more
-numbers. Such "numbers" are now parsed as strings composed of the
-specified ordinals.
+Formerly, if you wanted to mark a subroutine as being a method call or
+as requiring an automatic lock() when it is entered, you had to declare
+that with a C<use attrs> pragma in the body of the subroutine.
+That can now be accomplished with declaration syntax, like this:
-For example, C<print 97.98.99> used to output C<97.9899> in earlier
-versions, but now prints C<abc>.
+ sub mymethod : locked method ;
+ ...
+ sub mymethod : locked method {
+ ...
+ }
-See L<Support for strings represented as a vector of ordinals> below.
+ sub othermethod :locked :method ;
+ ...
+ sub othermethod :locked :method {
+ ...
+ }
-=item Possibly changed pseudo-random number generator
-In 5.005_0x and earlier, perl's rand() function used the C library
-rand(3) function. As of 5.005_52, Configure tests for drand48(),
-random(), and rand() (in that order) and picks the first one it finds.
-Perl programs that depend on reproducing a specific set of pseudo-random
-numbers will now likely produce different output. You can use
-C<sh Configure -Drandfunc=rand> to obtain the old behavior.
+(Note how only the first C<:> is mandatory, and whitespace surrounding
+the C<:> is optional.)
-=item Hashing function for hash keys has changed
+F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
+with the stubs they provide. See L<attributes>.
-Perl hashes are not order preserving. The apparently random order
-encountered when iterating on the contents of a hash is determined
-by the hashing algorithm used. To improve the distribution of lower
-bits in the hashed value, the algorithm has changed slightly as of
-5.005_52. When iterating over hashes, this may yield a random order
-that is B<different> from that of previous versions.
+=head2 File and directory handles can be autovivified
-=item C<undef> fails on read only values
+Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
+handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
+socket(), and accept()) now autovivify a file or directory handle
+if the handle passed to them is an uninitialized scalar variable. This
+allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
+to be used to create filehandles that will conveniently be closed
+automatically when the scope ends, provided there are no other references
+to them. This largely eliminates the need for typeglobs when opening
+filehandles that must be passed around, as in the following example:
-Using the C<undef> operator on a readonly value (such as $1) has
-the same effect as assigning C<undef> to the readonly value--it
-throws an exception.
+ sub myopen {
+ open my $fh, "@_"
+ or die "Can't open '@_': $!";
+ return $fh;
+ }
-=item Close-on-exec bit may be set on pipe and socket handles
+ {
+ my $f = myopen("</etc/motd");
+ print <$f>;
+ # $f implicitly closed here
+ }
-On systems that support a close-on-exec flag on filehandles, the
-flag will be set for any handles created by pipe(), socketpair(),
-socket(), and accept(), if that is warranted by the value of $^F
-that may be in effect. Earlier versions neglected to set the flag
-for handles created with these operators. See L<perlfunc/pipe>,
-L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
-and L<perlvar/$^F>.
+=head2 open() with more than two arguments
-=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
+If open() is passed three arguments instead of two, the second argument
+is used as the mode and the third argument is taken to be the file name.
+This is primarily useful for protecting against unintended magic behavior
+of the traditional two-argument form. See L<perlfunc/open>.
-Perl 5.004 deprecated the interpretation of C<$$1> and
-similar within interpolated strings to mean C<$$ . "1">,
-but still allowed it.
+=head2 64-bit support
-In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
+Any platform that has 64-bit integers either
-=item delete(), values() and C<\(%h)> operate on aliases to values, not copies
+ (1) natively as longs or ints
+ (2) via special compiler flags
+ (3) using long long or int64_t
-delete(), each(), values() and hashes in a list context return the actual
-values in the hash, instead of copies (as they used to in earlier
-versions). Typical idioms for using these constructs copy the
-returned values, but this can make a significant difference when
-creating references to the returned values.
+is able to use "quads" (64-bit integers) as follows:
-Keys in the hash are still returned as copies when iterating on
-a hash.
+=over 4
-=item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
+=item *
-vec() generates a run-time error if the BITS argument is not
-a valid power-of-two integer.
+constants (decimal, hexadecimal, octal, binary) in the code
-=item Text of some diagnostic output has changed
+=item *
-Most references to internal Perl operations in diagnostics
-have been changed to be more descriptive. This may be an
-issue for programs that may incorrectly rely on the exact
-text of diagnostics for proper functioning.
+arguments to oct() and hex()
-=item C<%@> has been removed
+=item *
-The undocumented special variable C<%@> that used to accumulate
-"background" errors (such as those that happen in DESTROY())
-has been removed, because it could potentially result in memory
-leaks.
+arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
-=item Parenthesized not() behaves like a list operator
+=item *
-The C<not> operator now falls under the "if it looks like a function,
-it behaves like a function" rule.
+printed as such
-As a result, the parenthesized form can be used with C<grep> and C<map>.
-The following construct used to be a syntax error before, but it works
-as expected now:
+=item *
- grep not($_), @things;
+pack() and unpack() "q" and "Q" formats
-On the other hand, using C<not> with a literal list slice may not
-work. The following previously allowed construct:
+=item *
- print not (1,2,3)[0];
+in basic arithmetics: + - * / % (NOTE: operating close to the limits
+of the integer values may produce surprising results)
-needs to be written with additional parentheses now:
+=item *
- print not((1,2,3)[0]);
+in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
+to be 32 bits wide but now operate on the full native width.)
-The behavior remains unaffected when C<not> is not followed by parentheses.
+=item *
-=item Semantics of bareword prototype C<(*)> have changed
+vec()
-Arguments prototyped as C<*> will now be visible within the subroutine
-as either a simple scalar or as a reference to a typeglob. Perl 5.005
-always coerced simple scalar arguments to a typeglob, which wasn't useful
-in situations where the subroutine must distinguish between a simple
-scalar and a typeglob. See L<perlsub/Prototypes>.
+=back
-=head2 On 64-bit platforms the semantics of bit operators have changed
+Note that unless you have the case (a) you will have to configure
+and compile Perl using the -Duse64bitint Configure flag.
-If your platform is either natively 64-bit or your Perl has been
-configured to used 64-bit integers (say C<perl -V> and see what is
-your ivsize: if it is 8, you are 64-bit) , be warned that the
-semantics of all the bitwise numeric operators (& | ^ ~ << >>) have
-been changed. They used to be forced to be 32 bits wide, but now in
-the aforementioned platforms they are 64 bits wide. Most dramatically
-this affects the unary ~: what used to be 32 bits wide, is now 64 bits
-wide. If you depend on your integers being 32 bits wide, mask off the
-excess bits with C<& 0xffffffff>.
+ NOTE: The Configure flags -Duselonglong and -Duse64bits have been
+ deprecated. Use -Duse64bitint instead.
-=back
+There are actually two modes of 64-bitness: the first one is achieved
+using Configure -Duse64bitint and the second one using Configure
+-Duse64bitall. The difference is that the first one is minimal and
+the second one maximal. The first works in more places than the second.
+
+The C<use64bitint> does only as much as is required to get 64-bit
+integers into Perl (this may mean, for example, using "long longs")
+while your memory may still be limited to 2 gigabytes (because your
+pointers could still be 32-bit). Note that the name C<64bitint> does
+not imply that your C compiler will be using 64-bit C<int>s (it might,
+but it doesn't have to): the C<use64bitint> means that you will be
+able to have 64 bits wide scalar values.
+
+The C<use64bitall> goes all the way by attempting to switch also
+integers (if it can), longs (and pointers) to being 64-bit. This may
+create an even more binary incompatible Perl than -Duse64bitint: the
+resulting executable may not run at all in a 32-bit box, or you may
+have to reboot/reconfigure/rebuild your operating system to be 64-bit
+aware.
-=head2 C Source Incompatibilities
+Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
+nor -Duse64bitall.
-=over 4
+Last but not least: note that due to Perl's habit of always using
+floating point numbers, the quads are still not true integers.
+When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
+-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
+are silently promoted to floating point numbers, after which they will
+start losing precision (in their lower digits).
-=item C<PERL_POLLUTE>
+ NOTE: 64-bit support is still experimental on most platforms.
+ Existing support only covers the LP64 data model. In particular, the
+ LLP64 data model is not yet supported. 64-bit libraries and system
+ APIs on many platforms have not stabilized--your mileage may vary.
-Release 5.005 grandfathered old global symbol names by providing preprocessor
-macros for extension source compatibility. As of release 5.6, these
-preprocessor definitions are not available by default. You need to explicitly
-compile perl with C<-DPERL_POLLUTE> to get these definitions. For
-extensions still using the old symbols, this option can be
-specified via MakeMaker:
+=head2 Large file support
- perl Makefile.PL POLLUTE=1
+If you have filesystems that support "large files" (files larger than
+2 gigabytes), you may now also be able to create and access them from
+Perl.
-=item C<PERL_IMPLICIT_CONTEXT>
+ NOTE: The default action is to enable large file support, if
+ available on the platform.
-PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
-with one of -Dusethreads, -Dusemultiplicity, or both. It is not
-intended to be enabled by users at this time.
+If the large file support is on, and you have a Fcntl constant
+O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
+of sysopen().
-This new build option provides a set of macros for all API functions
-such that an implicit interpreter/thread context argument is passed to
-every API function. As a result of this, something like C<sv_setsv(foo,bar)>
-amounts to a macro invocation that actually translates to something like
-C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
-to not have any significant source compatibility issues, the difference
-between a macro and a real function call will need to be considered.
+Beware that unless your filesystem also supports "sparse files" seeking
+to umpteen petabytes may be inadvisable.
-This means that there B<is> a source compatibility issue as a result of
-this if your extensions attempt to use pointers to any of the Perl API
-functions.
+Note that in addition to requiring a proper file system to do large
+files you may also need to adjust your per-process (or your
+per-system, or per-process-group, or per-user-group) maximum filesize
+limits before running Perl scripts that try to handle large files,
+especially if you intend to write such files.
-Note that the above issue is not relevant to the default build of
-Perl, whose interfaces continue to match those of prior versions
-(but subject to the other options described here).
+Finally, in addition to your process/process group maximum filesize
+limits, you may have quota limits on your filesystems that stop you
+(your user id or your user group id) from using large files.
-See L<perlguts/"The Perl API"> for detailed information on the
-ramifications of building Perl using this option.
+Adjusting your process/user/group/file system/operating system limits
+is outside the scope of Perl core language. For process limits, you
+may try increasing the limits using your shell's limits/limit/ulimit
+command before running Perl. The BSD::Resource extension (not
+included with the standard Perl distribution) may also be of use, it
+offers the getrlimit/setrlimit interface that can be used to adjust
+process resource usage limits, including the maximum filesize limit.
-=item C<PERL_POLLUTE_MALLOC>
+=head2 Long doubles
-Enabling Perl's malloc in release 5.005 and earlier caused
-the namespace of system versions of the malloc family of functions to
-be usurped by the Perl versions, since by default they used the
-same names.
+In some systems you may be able to use long doubles to enhance the
+range and precision of your double precision floating point numbers
+(that is, Perl's numbers). Use Configure -Duselongdouble to enable
+this support (if it is available).
-Besides causing problems on platforms that do not allow these functions to
-be cleanly replaced, this also meant that the system versions could not
-be called in programs that used Perl's malloc. Previous versions of Perl
-have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
-EMBEDMYMALLOC preprocessor definitions.
+=head2 "more bits"
-As of release 5.6, Perl's malloc family of functions have default names
-distinct from the system versions. You need to explicitly compile perl with
-C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
-and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
-the default.
+You can "Configure -Dusemorebits" to turn on both the 64-bit support
+and the long double support.
-Note that these functions do B<not> constitute Perl's memory allocation API.
-See L<perlguts/"Memory Allocation"> for further information about that.
+=head2 Enhanced support for sort() subroutines
-=back
+Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can
+now be used as sort subroutines. In either case, the two elements to
+be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
-=head2 Compatible C Source API Changes
+For unprototyped sort subroutines, the historical behavior of passing
+the elements to be compared as the global variables $a and $b remains
+unchanged.
-=over
+=head2 C<sort $coderef @foo> allowed
-=item C<PATCHLEVEL> is now C<PERL_VERSION>
+sort() did not accept a subroutine reference as the comparison
+function in earlier versions. This is now permitted.
-The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
-are now available by default from perl.h, and reflect the base revision,
-patchlevel, and subversion respectively. C<PERL_REVISION> had no
-prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
-previously available as C<PATCHLEVEL> and C<SUBVERSION>.
+=head2 File globbing implemented internally
-The new names cause less pollution of the B<cpp> namespace and reflect what
-the numbers have come to stand for in common practice. For compatibility,
-the old names are still supported when F<patchlevel.h> is explicitly
-included (as required before), so there is no source incompatibility
-from the change.
+Perl now uses the File::Glob implementation of the glob() operator
+automatically. This avoids using an external csh process and the
+problems associated with it.
-=item Support for C++ exceptions
+ NOTE: This is currently an experimental feature. Interfaces and
+ implementation are subject to change.
-change#3386, also needs perlguts documentation
-[TODO - Chip Salzenberg <chip@perlsupport.com>]
+=item Support for CHECK blocks
-=back
+In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
+subroutines named C<CHECK> are now special. These are queued up during
+compilation and behave similar to END blocks, except they are called at
+the end of compilation rather than at the end of execution. They cannot
+be called directly.
-=head2 Binary Incompatibilities
+=head2 POSIX character class syntax [: :] supported
-In general, the default build of this release is expected to be binary
-compatible for extensions built with the 5.005 release or its maintenance
-versions. However, specific platforms may have broken binary compatibility
-due to changes in the defaults used in hints files. Therefore, please be
-sure to always check the platform-specific README files for any notes to
-the contrary.
+For example to match alphabetic characters use /[[:alpha:]]/.
+See L<perlre> for details.
-The usethreads or usemultiplicity builds are B<not> binary compatible
-with the corresponding builds in 5.005.
+=item Better pseudo-random number generator
-On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
-among others), purely internal symbols such as parser functions and the
-run time opcodes are not exported by default. Perl 5.005 used to export
-all functions irrespective of whether they were considered part of the
-public API or not.
+In 5.005_0x and earlier, perl's rand() function used the C library
+rand(3) function. As of 5.005_52, Configure tests for drand48(),
+random(), and rand() (in that order) and picks the first one it finds.
-For the full list of public API functions, see L<perlapi>.
+These changes should result in better random numbers from rand().
-=head1 Installation and Configuration Improvements
+=head2 Improved C<qw//> operator
-=head2 -Dusethreads means something different
+The C<qw//> operator is now evaluated at compile time into a true list
+instead of being replaced with a run time call to C<split()>. This
+removes the confusing misbehaviour of C<qw//> in scalar context, which
+had inherited that behaviour from split().
-WARNING: Support for threads continues to be an experimental feature.
-Interfaces and implementation are subject to sudden and drastic changes.
+Thus:
-The -Dusethreads flag now enables the experimental interpreter-based thread
-support by default. To get the flavor of experimental threads that was in
-5.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
+ $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
-As of v5.5.640, interpreter-threads support is still lacking a way to
-create new threads from Perl (i.e., C<use Thread;> will not work with
-interpreter threads). C<use Thread;> continues to be available when you
-ask for use5005threads, bugs and all.
+now correctly prints "3|a", instead of "2|a".
-=head2 New Configure flags
+=item Better worst-case behavior of hashes
-The following new flags may be enabled on the Configure command line
-by running Configure with C<-Dflag>.
+Small changes in the hashing algorithm have been implemented in
+order to improve the distribution of lower order bits in the
+hashed value. This is expected to yield better performance on
+keys that are repeated sequences.
- usemultiplicity
- usethreads useithreads (new interpreter threads: no Perl API yet)
- usethreads use5005threads (threads as they were in 5.005)
+=head2 pack() format 'Z' supported
- use64bitint (equal to now deprecated 'use64bits')
- use64bitall
+The new format type 'Z' is useful for packing and unpacking null-terminated
+strings. See L<perlfunc/"pack">.
- uselongdouble
- usemorebits
- uselargefiles
- usesocks (only SOCKS v5 supported)
+=head2 pack() format modifier '!' supported
-=head2 Threadedness and 64-bitness now more daring
+The new format type modifier '!' is useful for packing and unpacking
+native shorts, ints, and longs. See L<perlfunc/"pack">.
-The Configure options enabling the use of threads and the use of
-64-bitness are now more daring in the sense that they no more have an
-explicit list of operating systems of known threads/64-bit
-capabilities. In other words: if your operating system has the
-necessary APIs and datatypes, you should be able just to go ahead and
-use them, for threads by Configure -Dusethreads, and for 64 bits
-either explicitly by Configure -Duse64bitint or implicitly if your
-system has 64 bit wide datatypes. See also L<"64-bit support">.
+=head2 pack() and unpack() support counted strings
-=head2 Long Doubles
+The template character '/' can be used to specify a counted string
+type to be packed or unpacked. See L<perlfunc/"pack">.
-Some platforms have "long doubles", floating point numbers of even
-larger range than ordinary "doubles". To enable using long doubles for
-Perl's scalars, use -Duselongdouble.
+=head2 Comments in pack() templates
-=head2 -Dusemorebits
+The '#' character in a template introduces a comment up to
+end of the line. This facilitates documentation of pack()
+templates.
-You can enable both -Duse64bitint and -Dlongdouble by -Dusemorebits.
-See also L<"64-bit support">.
+=head2 Weak references
-=head2 -Duselargefiles
+In previous versions of Perl, you couldn't cache objects so as
+to allow them to be deleted if the last reference from outside
+the cache is deleted. The reference in the cache would hold a
+reference count on the object and the objects would never be
+destroyed.
-Some platforms support large files, files larger than two gigabytes.
-See L<"Large file support"> for more information.
+Another familiar problem is with circular references. When an
+object references itself, its reference count would never go
+down to zero, and it would not get destroyed until the program
+is about to exit.
-=head2 installusrbinperl
+Weak references solve this by allowing you to "weaken" any
+reference, that is, make it not count towards the reference count.
+When the last non-weak reference to an object is deleted, the object
+is destroyed and all the weak references to the object are
+automatically undef-ed.
-You can use "Configure -Uinstallusrbinperl" which causes installperl
-to skip installing perl also as /usr/bin/perl. This is useful if you
-prefer not to modify /usr/bin for some reason or another but harmful
-because many scripts assume to find Perl in /usr/bin/perl.
+To use this feature, you need the WeakRef package from CPAN, which
+contains additional documentation.
-=head2 SOCKS support
+ NOTE: This is an experimental feature. Details are subject to change.
-You can use "Configure -Dusesocks" which causes Perl to probe
-for the SOCKS (v5, not v4) proxy protocol library,
-http://www.socks.nec.com/
+=head2 Binary numbers supported
-=head2 C<-A> flag
+Binary numbers are now supported as literals, in s?printf formats, and
+C<oct()>:
-You can "post-edit" the Configure variables using the Configure C<-A>
-flag. The editing happens immediately after the platform specific
-hints files have been processed but before the actual configuration
-process starts. Run C<Configure -h> to find out the full C<-A> syntax.
+ $answer = 0b101010;
+ printf "The answer is: %b\n", oct("0b101010");
-=head2 Enhanced Installation Directories
+=head2 Lvalue subroutines
-The installation structure has been enriched to improve the support
-for maintaining multiple versions of perl, to provide locations for
-vendor-supplied modules, scripts, and manpages, and to ease maintenance
-of locally-added modules, scripts, and manpages. See the section on
-Installation Directories in the INSTALL file for complete details.
-For most users building and installing from source, the defaults should
-be fine.
+Subroutines can now return modifiable lvalues.
+See L<perlsub/"Lvalue subroutines">.
-If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
-special values for library directories, you might wish to consider using
-the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
-config.sh file from an earlier version of perl, you should be sure to
-check that Configure makes sensible choices for the new directories.
-See INSTALL for complete details.
+ NOTE: This is an experimental feature. Details are subject to change.
-=head1 Core Changes
+=head2 Some arrows may be omitted in calls through references
-=head2 Unicode and UTF-8 support
+Perl now allows the arrow to be omitted in many constructs
+involving subroutine calls through references. For example,
+C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
+This is rather similar to how the arrow may be omitted from
+C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
+required for C<< foo(10)->('bar') >>.
-Perl can optionally use UTF-8 as its internal representation for character
-strings. The C<utf8> and C<bytes> pragmas are used to control this support
-in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
-more information.
+=head2 Boolean assignment operators are legal lvalues
-=head2 Interpreter cloning, threads, and concurrency
+Constructs such as C<($a ||= 2) += 1> are now allowed.
-WARNING: This is an experimental feature in a pre-alpha state. Use
-at your own risk.
+=head2 exists() is supported on subroutine names
-Perl 5.005_63 introduces the beginnings of support for running multiple
-interpreters concurrently in different threads. In conjunction with
-the perl_clone() API call, which can be used to selectively duplicate
-the state of any given interpreter, it is possible to compile a
-piece of code once in an interpreter, clone that interpreter
-one or more times, and run all the resulting interpreters in distinct
-threads.
+The exists() builtin now works on subroutine names. A subroutine
+is considered to exist if it has been declared (even if implicitly).
+See L<perlfunc/exists> for examples.
-On Windows, this feature is used to emulate fork() at the interpreter
-level. See L<perlfork>.
+=head2 exists() and delete() are supported on array elements
-This feature is still in evolution. It is eventually meant to be used
-to selectively clone a subroutine and data reachable from that
-subroutine in a separate interpreter and run the cloned subroutine
-in a separate thread. Since there is no shared data between the
-interpreters, little or no locking will be needed (unless parts of
-the symbol table are explicitly shared). This is obviously intended
-to be an easy-to-use replacement for the existing threads support.
+The exists() and delete() builtins now work on simple arrays as well.
+The behavior is similar to that on hash elements.
-Support for cloning interpreters and interpreter concurrency can be
-enabled using the -Dusethreads Configure option (see win32/Makefile for
-how to enable it on Windows.) The resulting perl executable will be
-functionally identical to one that was built with -Dmultiplicity, but
-the perl_clone() API call will only be available in the former.
+exists() can be used to check whether an array element has been
+initialized. This avoids autovivifying array elements that don't exist.
+If the array is tied, the EXISTS() method in the corresponding tied
+package will be invoked.
+
+delete() may be used to remove an element from the array and return
+it. The array element at that position returns to its unintialized
+state, so that testing for the same element with exists() will return
+false. If the element happens to be the one at the end, the size of
+the array also shrinks up to the highest element that tests true for
+exists(), or 0 if none such is found. If the array is tied, the DELETE()
+method in the corresponding tied package will be invoked.
--Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
-Perl source code changes that provide a clear separation between the op tree
-and the data it operates with. The former is considered immutable, and can
-therefore be shared between an interpreter and all of its clones, while the
-latter is considered local to each interpreter, and is therefore copied for
-each clone.
+See L<perlfunc/exists> and L<perlfunc/delete> for examples.
-Note that building Perl with the -Dusemultiplicity Configure option
-is adequate if you wish to run multiple B<independent> interpreters
-concurrently in different threads. -Dusethreads only provides the
-additional functionality of the perl_clone() API call and other
-support for running B<cloned> interpreters concurrently.
+=head2 Pseudo-hashes work better
-[XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
-enabled.]
+Dereferencing some types of reference values in a pseudo-hash,
+such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
+been corrected.
-=head2 Lexically scoped warning categories
+When applied to a pseudo-hash element, exists() now reports whether
+the specified value exists, not merely if the key is valid.
-You can now control the granularity of warnings emitted by perl at a finer
-level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
-for details.
+delete() now works on pseudo-hashes. When given a pseudo-hash element
+or slice it deletes the values corresponding to the keys (but not the keys
+themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
+
+Pseudo-hash slices with constant keys are now optimized to array lookups
+at compile-time.
+
+List assignments to pseudo-hash slices are now supported.
+
+The C<fields> pragma now provides ways to create pseudo-hashes, via
+fields::new() and fields::phash(). See L<fields>.
+
+ NOTE: The pseudo-hash data type continues to be experimental.
+ Limiting oneself to the interface elements provided by the
+ fields pragma will provide protection from any future changes.
+
+=head2 Automatic flushing of output buffers
+
+fork(), exec(), system(), qx//, and pipe open()s now flush buffers
+of all files opened for output when the operation was attempted. This
+mostly eliminates confusing buffering mishaps suffered by users unaware
+of how Perl internally handles I/O.
+
+This is not supported on some platforms like Solaris where a suitably
+correct implementation of fflush(NULL) isn't available.
+
+=head2 Better diagnostics on meaningless filehandle operations
+
+Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
+are compile time errors. Attempting to read from filehandles that
+were opened only for writing will now produce warnings (just as
+writing to read-only filehandles does).
+
+=head2 Where possible, buffered data discarded from duped input filehandle
+
+C<< open(NEW, "<&OLD") >> now attempts to discard any data that
+was previously read and buffered in C<OLD> before duping the handle.
+On platforms where doing this is allowed, the next read operation
+on C<NEW> will return the same data as the corresponding operation
+on C<OLD>. Formerly, it would have returned the data from the start
+of the following disk block instead.
+
+=head2 eof() has the same old magic as <>
+
+C<eof()> would return true if no attempt to read from C<< <> >> had
+yet been made. C<eof()> has been changed to have a little magic of its
+own, it now opens the C<< <> >> files.
+
+=head2 binmode() can be used to set :crlf and :raw modes
+
+binmode() now accepts a second argument that specifies a discipline
+for the handle in question. The two pseudo-disciplines ":raw" and
+":crlf" are currently supported on DOS-derivative platforms.
+See L<perlfunc/"binmode"> and L<open>.
+
+=head2 C<-T> filetest recognizes UTF-8 encoded files as "text"
+
+The algorithm used for the C<-T> filetest has been enhanced to
+correctly identify UTF-8 content as "text".
+
+=head2 system(), backticks and pipe open now reflect exec() failure
+
+On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
+etc., are implemented via fork() and exec(). When the underlying
+exec() fails, earlier versions did not report the error properly,
+since the exec() happened to be in a different process.
+
+The child process now communicates with the parent about the
+error in launching the external command, which allows these
+constructs to return with their usual error value and set $!.
+
+=head2 Improved diagnostics
+
+Line numbers are no longer suppressed (under most likely circumstances)
+during the global destruction phase.
+
+Diagnostics emitted from code running in threads other than the main
+thread are now accompanied by the thread ID.
+
+Embedded null characters in diagnostics now actually show up. They
+used to truncate the message in prior versions.
+
+$foo::a and $foo::b are now exempt from "possible typo" warnings only
+if sort() is encountered in package C<foo>.
+
+Unrecognized alphabetic escapes encountered when parsing quote
+constructs now generate a warning, since they may take on new
+semantics in later versions of Perl.
+
+Many diagnostics now report the internal operation in which the warning
+was provoked, like so:
+
+ Use of uninitialized value in concatenation (.) at (eval 1) line 1.
+ Use of uninitialized value in print at (eval 1) line 1.
+
+Diagnostics that occur within eval may also report the file and line
+number where the eval is located, in addition to the eval sequence
+number and the line number within the evaluated text itself. For
+example:
+
+ Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
+
+=head2 Diagnostics follow STDERR
+
+Diagnostic output now goes to whichever file the C<STDERR> handle
+is pointing at, instead of always going to the underlying C runtime
+library's C<stderr>.
+
+=item More consistent close-on-exec behavior
+
+On systems that support a close-on-exec flag on filehandles, the
+flag is now set for any handles created by pipe(), socketpair(),
+socket(), and accept(), if that is warranted by the value of $^F
+that may be in effect. Earlier versions neglected to set the flag
+for handles created with these operators. See L<perlfunc/pipe>,
+L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
+and L<perlvar/$^F>.
+
+=head2 syswrite() ease-of-use
+
+The length argument of C<syswrite()> has become optional.
+
+=head2 Better syntax checks on parenthesized unary operators
+
+Expressions such as:
+
+ print defined(&foo,&bar,&baz);
+ print uc("foo","bar","baz");
+ undef($foo,&bar);
+
+used to be accidentally allowed in earlier versions, and produced
+unpredictable behaviour. Some produced ancillary warnings
+when used in this way; others silently did the wrong thing.
+
+The parenthesized forms of most unary operators that expect a single
+argument now ensure that they are not called with more than one
+argument, making the cases shown above syntax errors. The usual
+behaviour of:
+
+ print defined &foo, &bar, &baz;
+ print uc "foo", "bar", "baz";
+ undef $foo, &bar;
+
+remains unchanged. See L<perlop>.
+
+=head2 Bit operators support full native integer width
+
+The bit operators (& | ^ ~ << >>) now operate on the full native
+integral width (the exact size of which is available in $Config{ivsize}).
+For example, if your platform is either natively 64-bit or if Perl
+has been configured to use 64-bit integers, these operations apply
+to 8 bytes (as opposed to 4 bytes on 32-bit platforms).
+For portability, be sure to mask off the excess bits in the result of
+unary C<~>, e.g., C<~$x & 0xffffffff>.
+
+=head2 Improved security features
+
+More potentially unsafe operations taint their results for improved
+security.
+
+The C<passwd> and C<shell> fields returned by the getpwent(), getpwnam(),
+and getpwuid() are now tainted, because the user can affect their own
+encrypted password and login shell.
+
+The variable modified by shmread(), and messages returned by msgrcv()
+(and its object-oriented interface IPC::SysV::Msg::rcv) are also tainted,
+because other untrusted processes can modify messages and shared memory
+segments for their own nefarious purposes.
+
+=item More functional bareword prototype (*)
+
+Bareword prototypes have been rationalized to enable them to be used
+to override builtins that accept barewords and interpret them in
+a special way, such as C<require> or C<do>.
+
+Arguments prototyped as C<*> will now be visible within the subroutine
+as either a simple scalar or as a reference to a typeglob.
+See L<perlsub/Prototypes>.
+
+=head2 C<require> and C<do> may be overridden
+
+C<require> and C<do 'file'> operations may be overridden locally
+by importing subroutines of the same name into the current package
+(or globally by importing them into the CORE::GLOBAL:: namespace).
+Overriding C<require> will also affect C<use>, provided the override
+is visible at compile-time.
+See L<perlsub/"Overriding Built-in Functions">.
+
+=head2 $^X variables may now have names longer than one character
+
+Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
+error. Now variable names that begin with a control character may be
+arbitrarily long. However, for compatibility reasons, these variables
+I<must> be written with explicit braces, as C<${^XY}> for example.
+C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
+than one control character, such as C<${^XY^Z}>, are illegal.
+
+The old syntax has not changed. As before, `^X' may be either a
+literal control-X character or the two-character sequence `caret' plus
+`X'. When braces are omitted, the variable name stops after the
+control character. Thus C<"$^XYZ"> continues to be synonymous with
+C<$^X . "YZ"> as before.
+
+As before, lexical variables may not have names beginning with control
+characters. As before, variables whose names begin with a control
+character are always forced to be in package `main'. All such variables
+are reserved for future extensions, except those that begin with
+C<^_>, which may be used by user programs and are guaranteed not to
+acquire special meaning in any future version of Perl.
+
+=head2 New variable $^C reflects C<-c> switch
+
+C<$^C> has a boolean value that reflects whether perl is being run
+in compile-only mode (i.e. via the C<-c> switch). Since
+BEGIN blocks are executed under such conditions, this variable
+enables perl code to determine whether actions that make sense
+only during normal running are warranted. See L<perlvar>.
+
+=head2 New variable $^V contains Perl version as a string
+
+C<$^V> contains the Perl version number as a string composed of
+characters whose ordinals match the version numbers, i.e. v5.6.0.
+This may be used in string comparisons.
+
+See C<Support for strings represented as a vector of ordinals> for an
+example.
+
+=head2 Optional Y2K warnings
+
+If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
+it emits optional warnings when concatenating the number 19
+with another number.
+
+This behavior must be specifically enabled when running Configure.
+See F<INSTALL> and F<README.Y2K>.
+
+=head1 Modules and Pragmata
+
+=head2 Modules
+
+=over 4
+
+=item attributes
+
+While used internally by Perl as a pragma, this module also
+provides a way to fetch subroutine and variable attributes.
+See L<attributes>.
+
+=item B
+
+The Perl Compiler suite has been extensively reworked for this
+release. More of the standard Perl testsuite passes when run
+under the Compiler, but there is still a significant way to
+go to achieve production quality compiled executables.
+
+ NOTE: The Compiler suite remains highly experimental. The
+ generated code may not be correct, even it manages to execute
+ without errors.
+
+=item Benchmark
+
+Overall, Benchmark results exhibit lower average error and better timing
+accuracy.
+
+You can now run tests for I<n> seconds instead of guessing the right
+number of tests to run: e.g., timethese(-5, ...) will run each
+code for at least 5 CPU seconds. Zero as the "number of repetitions"
+means "for at least 3 CPU seconds". The output format has also
+changed. For example:
+
+ use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
+
+will now output something like this:
+
+ Benchmark: running a, b, each for at least 5 CPU seconds...
+ a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
+ b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
+
+New features: "each for at least N CPU seconds...", "wallclock secs",
+and the "@ operations/CPU second (n=operations)".
+
+timethese() now returns a reference to a hash of Benchmark objects containing
+the test results, keyed on the names of the tests.
+
+timethis() now returns the iterations field in the Benchmark result object
+instead of 0.
+
+timethese(), timethis(), and the new cmpthese() (see below) can also take
+a format specifier of 'none' to suppress output.
+
+A new function countit() is just like timeit() except that it takes a
+TIME instead of a COUNT.
+
+A new function cmpthese() prints a chart comparing the results of each test
+returned from a timethese() call. For each possible pair of tests, the
+percentage speed difference (iters/sec or seconds/iter) is shown.
+
+For other details, see L<Benchmark>.
+
+=item ByteLoader
+
+The ByteLoader is a dedicated extension to generate and run
+Perl bytecode. See L<ByteLoader>.
-=head2 Lvalue subroutines
+=item constant
-WARNING: This is an experimental feature.
+References can now be used.
-change#4081
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
-Tuomas Lukka <lukka@iki.fi>)]
+The new version also allows a leading underscore in constant names, but
+disallows a double leading underscore (as in "__LINE__"). Some other names
+are disallowed or warned against, including BEGIN, END, etc. Some names
+which were forced into main:: used to fail silently in some cases; now they're
+fatal (outside of main::) and an optional warning (inside of main::).
+The ability to detect whether a constant had been set with a given name has
+been added.
-=head2 "our" declarations
+See L<constant>.
-An "our" declaration introduces a value that can be best understood
-as a lexically scoped symbolic alias to a global variable in the
-package that was current where the variable was declared. This is
-mostly useful as an alternative to the C<vars> pragma, but also provides
-the opportunity to introduce typing and other attributes for such
-variables. See L<perlfunc/our>.
+=item charnames
-=head2 Support for strings represented as a vector of ordinals
+This pragma implements the C<\N> string escape. See L<charnames>.
-Literals of the form C<v1.2.3.4> are now parsed as a string composed of
-of characters with the specified ordinals. This is an alternative, more
-readable way to construct (possibly unicode) strings instead of
-interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
-C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
-parsed the same as C<v1.2.3>.
+=item Data::Dumper
-Strings written in this form are also useful to represent version "numbers".
-It is easy to compare such version "numbers" (which are really just plain
-strings) using any of the usual string comparison operators C<eq>, C<ne>,
-C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
-C<&>, etc.
+A C<Maxdepth> setting can be specified to avoid venturing
+too deeply into deep data structures. See L<Data::Dumper>.
-In conjunction with the new C<$^V> magic variable (which contains
-the perl version as a string), such literals can be used as a readable way
-to check if you're running a particular version of Perl:
+The XSUB implementation of Dump() is now automatically called if the
+C<Useqq> setting is not in use.
- # this will parse in older versions of Perl also
- if ($^V and $^V gt v5.5.640) {
- # new features supported
- }
+Dumping C<qr//> objects works correctly.
-C<require> and C<use> also have some special magic to support such literals.
-They will be interpreted as a version rather than as a module name:
+=item DB
- require v5.6.0; # croak if $^V lt v5.6.0
- use v5.6.0; # same, but croaks at compile-time
+C<DB> is an experimental module that exposes a clean abstraction
+to Perl's debugging API.
-Alternatively, the C<v> may be omitted if there is more than one dot:
+=item DB_File
- require 5.6.0;
- use 5.6.0;
+DB_File can now be built with Berkeley DB versions 1, 2 or 3.
+See C<ext/DB_File/Changes>.
-Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
-to print ordinals of characters in arbitrary strings:
+=item Devel::DProf
- printf "v%vd", $^V; # prints current version, such as "v5.5.650"
- printf "%*vX", ":", $addr; # formats IPv6 address
- printf "%*vb", " ", $bits; # displays bitstring
+Devel::DProf, a Perl source code profiler has been added. See
+L<Devel::DProf> and L<dprofpp>.
-See L<perldata/"Scalar value constructors"> for additional information.
+=item Devel::Peek
-=head2 Weak references
+The Devel::Peek module provides access to the internal representation
+of Perl variables and data. It is a data debugging tool for the XS programmer.
-WARNING: This is an experimental feature.
+=item Dumpvalue
-In previous versions of Perl, you couldn't cache objects so as
-to allow them to be deleted if the last reference from outside
-the cache is deleted. The reference in the cache would hold a
-reference count on the object and the objects would never be
-destroyed.
+The Dumpvalue module provides screen dumps of Perl data.
-Another familiar problem is with circular references. When an
-object references itself, its reference count would never go
-down to zero, and it would not get destroyed until the program
-is about to exit.
+=item DynaLoader
-Weak references solve this by allowing you to "weaken" any
-reference, that is, make it not count towards the reference count.
-When the last non-weak reference to an object is deleted, the object
-is destroyed and all the weak references to the object are
-automatically undef-ed.
+DynaLoader now supports a dl_unload_file() function on platforms that
+support unloading shared objects using dlclose().
-To use this feature, you need the WeakRef package from CPAN, which
-contains additional documentation.
+Perl can also optionally arrange to unload all extension shared objects
+loaded by Perl. To enable this, build Perl with the Configure option
+C<-Accflags=-DDL_UNLOAD_ALL_AT_EXIT>. (This maybe useful if you are
+using Apache with mod_perl.)
-change#3385, also need perlguts documentation
-[TODO - Tuomas Lukka <lukka@iki.fi>]
+=item English
-=head2 File globbing implemented internally
+$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
+(a numeric value).
-WARNING: This is currently an experimental feature. Interfaces and
-implementation are likely to change.
+=item Env
-Perl now uses the File::Glob implementation of the glob() operator
-automatically. This avoids using an external csh process and the
-problems associated with it.
+Env now supports accessing environment variables like PATH as array
+variables.
-=head2 Binary numbers supported
+=item Fcntl
-Binary numbers are now supported as literals, in s?printf formats, and
-C<oct()>:
+More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
+large file (more than 4GB) access (NOTE: the O_LARGEFILE is
+automatically added to sysopen() flags if large file support has been
+configured, as is the default), Free/Net/OpenBSD locking behaviour
+flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
+mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek()
+constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
+C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions
+are available via the C<:mode> tag.
- $answer = 0b101010;
- printf "The answer is: %b\n", oct("0b101010");
+=item File::Compare
-=head2 Some arrows may be omitted in calls through references
+A compare_text() function has been added, which allows custom
+comparison functions. See L<File::Compare>.
-Perl now allows the arrow to be omitted in many constructs
-involving subroutine calls through references. For example,
-C<$foo[10]-E<gt>('foo')> may now be written C<$foo[10]('foo')>.
-This is rather similar to how the arrow may be omitted from
-C<$foo[10]-E<gt>{'foo'}>. Note however, that the arrow is still
-required for C<foo(10)-E<gt>('bar')>.
+=item File::Find
-=head2 exists() is supported on subroutine names
+File::Find now works correctly when the wanted() function is either
+autoloaded or is a symbolic reference.
-The exists() builtin now works on subroutine names. A subroutine
-is considered to exist if it has been declared (even if implicitly).
-See L<perlfunc/exists> for examples.
+A bug that caused File::Find to lose track of the working directory
+when pruning top-level directories has been fixed.
-=head2 exists() and delete() are supported on array elements
+File::Find now also supports several other options to control its
+behavior. It can follow symbolic links if the C<follow> option is
+specified. Enabling the C<no_chdir> option will make File::Find skip
+changing the current directory when walking directories. The C<untaint>
+flag can be useful when running with taint checks enabled.
-The exists() and delete() builtins now work on simple arrays as well.
-The behavior is similar to that on hash elements.
+See L<File::Find>.
-exists() can be used to check whether an array element has been
-initialized. This avoids autovivifying array elements that don't exist.
-If the array is tied, the EXISTS() method in the corresponding tied
-package will be invoked.
+=item File::Glob
-delete() may be used to remove an element from the array and return
-it. The array element at that position returns to its unintialized
-state, so that testing for the same element with exists() will return
-false. If the element happens to be the one at the end, the size of
-the array also shrinks up to the highest element that tests true for
-exists(), or 0 if none such is found. If the array is tied, the DELETE()
-method in the corresponding tied package will be invoked.
+This extension implements BSD-style file globbing. By default,
+it will also be used for the internal implementation of the glob()
+operator. See L<File::Glob>.
-See L<perlfunc/exists> and L<perlfunc/delete> for examples.
+=item File::Spec
-=head2 syswrite() ease-of-use
+New methods have been added to the File::Spec module: devnull() returns
+the name of the null device (/dev/null on Unix) and tmpdir() the name of
+the temp directory (normally /tmp on Unix). There are now also methods
+to convert between absolute and relative filenames: abs2rel() and
+rel2abs(). For compatibility with operating systems that specify volume
+names in file paths, the splitpath(), splitdir(), and catdir() methods
+have been added.
-The length argument of C<syswrite()> has become optional.
+=item File::Spec::Functions
-=head2 File and directory handles can be autovivified
+The new File::Spec::Functions modules provides a function interface
+to the File::Spec module. Allows shorthand
-Similar to how constructs such as C<$x-E<gt>[0]> autovivify a reference,
-handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
-socket(), and accept()) now autovivify a file or directory handle
-if the handle passed to them is an uninitialized scalar variable. This
-allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
-to be used to create filehandles that will conveniently be closed
-automatically when the scope ends, provided there are no other references
-to them. This largely eliminates the need for typeglobs when opening
-filehandles that must be passed around, as in the following example:
+ $fullname = catfile($dir1, $dir2, $file);
- sub myopen {
- open my $fh, "@_"
- or die "Can't open '@_': $!";
- return $fh;
- }
+instead of
- {
- my $f = myopen("</etc/motd");
- print <$f>;
- # $f implicitly closed here
- }
+ $fullname = File::Spec->catfile($dir1, $dir2, $file);
-[TODO - this idiom needs more pod penetration]
+=item Getopt::Long
-=head2 64-bit support
+Getopt::Long licensing has changed to allow the Perl Artistic License
+as well as the GPL. It used to be GPL only, which got in the way of
+non-GPL applications that wanted to use Getopt::Long.
- NOTE: The Configure flags -Duselonglong and -Duse64bits
- have been deprecated. Use -Duse64bitint instead.
+Getopt::Long encourages the use of Pod::Usage to produce help
+messages. For example:
-Any platform that has 64-bit integers either (a) natively as longs or
-ints (b) via special compiler flags (c) using long long are able to
-use "quads" (64-integers) as follows:
+ use Getopt::Long;
+ use Pod::Usage;
+ my $man = 0;
+ my $help = 0;
+ GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
+ pod2usage(1) if $help;
+ pod2usage(-exitstatus => 0, -verbose => 2) if $man;
-=over 4
+ __END__
-=item *
+ =head1 NAME
-constants (decimal, hexadecimal, octal, binary) in the code
+ sample - Using GetOpt::Long and Pod::Usage
-=item *
+ =head1 SYNOPSIS
-arguments to oct() and hex()
+ sample [options] [file ...]
-=item *
+ Options:
+ -help brief help message
+ -man full documentation
-arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
+ =head1 OPTIONS
-=item *
+ =over 8
-printed as such
+ =item B<-help>
-=item *
+ Print a brief help message and exits.
-pack() and unpack() "q" and "Q" formats
+ =item B<-man>
-=item *
+ Prints the manual page and exits.
-in basic arithmetics: + - * / % (NOTE: operating close to the limits
-of the integer values may produce surprising results)
+ =back
-=item *
+ =head1 DESCRIPTION
-in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
-to be 32 bits wide.)
+ B<This program> will read the given input file(s) and do someting
+ useful with the contents thereof.
-=item *
+ =cut
-vec()
+See L<Pod::Usage> for details.
-=back
+A bug that prevented the non-option call-back <> from being
+specified as the first argument has been fixed.
-Note that unless you have the case (a) you will have to configure
-and compile Perl using the -Duse64bitint Configure flag.
+To specify the characters < and > as option starters, use ><. Note,
+however, that changing option starters is strongly deprecated.
-There are actually two modes of 64-bitness: the first one is achieved
-using Configure -Duse64bitint and the second one using Configure
--Duse64bitall. The difference is that the first one is minimal and
-the second one maximal. The first one does only as much as is
-required to get 64-bit integers into Perl (this may mean, for example,
-using "long longs") while your memory may still be limited to 2
-gigabytes (because your pointers most likely are 32-bit); the second
-one goes all the way by attempting to switch also longs (and pointers)
-being 64-bit. This may create an even more binary incompatible Perl
-than -Duse64bitint: the resulting executable may not run at all in a
-CPU-bit box, or you may have to reboot/reconfigure/rebuild your
-operating system to be 64-bit aware.
+=item IO
-Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
-nor -Duse64bitall.
+write() and syswrite() will now accept a single-argument
+form of the call, for consistency with Perl's syswrite().
-Last but not least: note that due to Perl's habit of always using
-floating point numbers the quads are still not true integers.
-When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
--9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
-are silently promoted to floating point numbers, after which they will
-start losing precision (their lower digits).
+You can now create a TCP-based IO::Socket::INET without forcing
+a connect attempt. This allows you to configure its options
+(like making it non-blocking) and then call connect() manually.
-=head2 Large file support
+A bug that prevented the IO::Socket::protocol() accessor
+from ever returning the correct value has been corrected.
-If you have filesystems that support "large files" (files larger than
-2 gigabytes), you may now also be able to create and access them from
-Perl. You have to use Configure -Duselargefiles. Turning on the
-large file support turns on also the 64-bit support on many platforms.
-Beware that unless your filesystem also supports "sparse files" seeking
-to umpteen petabytes may be unadvisable.
+IO::Socket::connect now uses non-blocking IO instead of alarm()
+to do connect timeouts.
-Note that in addition to requiring a proper file system to do large
-files you may also need to adjust your per-process (or your
-per-system, or per-process-group, or per-user-group) maximum filesize
-limits before running Perl scripts that try to handle large files,
-especially if you intend to write such files.
+IO::Socket::accept now uses select() instead of alarm() for doing
+timeouts.
-Finally, in addition to your process/process group maximum filesize
-limits, you may have quota limits on your filesystems that stop you
-(your user id or your user group id) from using large files.
+IO::Socket::INET->new now sets $! correctly on failure. $@ is
+still set for backwards compatability.
-Adjusting your process/user/group/file system/operating system limits
-is outside the scope of Perl core language. For process limits, you
-may try increasing the limits using your shell's limits/limit/ulimit
-command before running Perl. The BSD::Resource extension (not
-included with the standard Perl distribution) may also be of use, it
-offers the getrlimit/setrlimit interface that can be used to adjust
-process resource usage limits, including the maximum filesize limit.
+=item JPL
-=head2 Long doubles
+Java Perl Lingo is now distributed with Perl. See jpl/README
+for more information.
-In some systems you may be able to use long doubles to enhance the
-range and precision of your double precision floating point numbers
-(that is, Perl's numbers). Use Configure -Duselongdouble to enable
-this support (if it is available).
+=item lib
-=head2 "more bits"
+C<use lib> now weeds out any trailing duplicate entries.
+C<no lib> removes all named entries.
-You can "Configure -Dusemorebits" to turn on both the 64-bit support
-and the long double support.
+=item Math::BigInt
-=head2 Enhanced support for sort() subroutines
+The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
+and C<~> are now supported on bigints.
-Perl subroutines with a prototype of C<($$)> and XSUBs in general can
-now be used as sort subroutines. In either case, the two elements to
-be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
+=item Math::Complex
-For unprototyped sort subroutines, the historical behavior of passing
-the elements to be compared as the global variables $a and $b remains
-unchanged.
+The accessor methods Re, Im, arg, abs, rho, and theta can now also
+act as mutators (accessor $z->Re(), mutator $z->Re(3)).
-=head2 Better syntax checks on parenthesized unary operators
+The class method C<display_format> and the corresponding object method
+C<display_format>, in addition to accepting just one argument, now can
+also accept a parameter hash. Recognized keys of a parameter hash are
+C<"style">, which corresponds to the old one parameter case, and two
+new parameters: C<"format">, which is a printf()-style format string
+(defaults usually to C<"%.15g">, you can revert to the default by
+setting the format string to C<undef>) used for both parts of a
+complex number, and C<"polar_pretty_print"> (defaults to true),
+which controls whether an attempt is made to try to recognize small
+multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
+polar complex number.
+
+The potentially disruptive change is that in list context both methods
+now I<return the parameter hash>, instead of only the value of the
+C<"style"> parameter.
-Expressions such as:
+=item Math::Trig
- print defined(&foo,&bar,&baz);
- print uc("foo","bar","baz");
- undef($foo,&bar);
+A little bit of radial trigonometry (cylindrical and spherical),
+radial coordinate conversions, and the great circle distance were added.
-used to be accidentally allowed in earlier versions, and produced
-unpredictable behaviour. Some produced ancillary warnings
-when used in this way; others silently did the wrong thing.
+=item Pod::Parser, Pod::InputObjects
-The parenthesized forms of most unary operators that expect a single
-argument now ensure that they are not called with more than one
-argument, making the cases shown above syntax errors. The usual
-behaviour of:
+Pod::Parser is a base class for parsing and selecting sections of
+pod documentation from an input stream. This module takes care of
+identifying pod paragraphs and commands in the input and hands off the
+parsed paragraphs and commands to user-defined methods which are free
+to interpret or translate them as they see fit.
- print defined &foo, &bar, &baz;
- print uc "foo", "bar", "baz";
- undef $foo, &bar;
+Pod::InputObjects defines some input objects needed by Pod::Parser, and
+for advanced users of Pod::Parser that need more about a command besides
+its name and text.
-remains unchanged. See L<perlop>.
+As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
+"base parser code" recommended for use by all pod2xxx translators.
+Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
+to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
+underway. For any questions or comments about pod parsing and translating
+issues and utilities, please use the pod-people@perl.org mailing list.
-=head2 POSIX character class syntax [: :] supported
+For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
-For example to match alphabetic characters use /[[:alpha:]]/.
-See L<perlre> for details.
+=item Pod::Checker, podchecker
-=head2 Improved C<qw//> operator
+This utility checks pod files for correct syntax, according to
+L<perlpod>. Obvious errors are flagged as such, while warnings are
+printed for mistakes that can be handled gracefully. The checklist is
+not complete yet. See L<Pod::Checker>.
-The C<qw//> operator is now evaluated at compile time into a true list
-instead of being replaced with a run time call to C<split()>. This
-removes the confusing misbehaviour of C<qw//> in scalar context, which
-had inherited that behaviour from split().
+=item Pod::ParseUtils, Pod::Find
-Thus:
+These modules provide a set of gizmos that are useful mainly for pod
+translators. L<Pod::Find|Pod::Find> traverses directory structures and
+returns found pod files, along with their canonical names (like
+C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
+B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
+(for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
+(for caching information about pod files, e.g., link nodes).
- $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
+=item Pod::Select, podselect
-now correctly prints "3|a", instead of "2|a".
+Pod::Select is a subclass of Pod::Parser which provides a function
+named "podselect()" to filter out user-specified sections of raw pod
+documentation from an input stream. podselect is a script that provides
+access to Pod::Select from other scripts to be used as a filter.
+See L<Pod::Select>.
-=head2 pack() format 'Z' supported
+=item Pod::Usage, pod2usage
-The new format type 'Z' is useful for packing and unpacking null-terminated
-strings. See L<perlfunc/"pack">.
+Pod::Usage provides the function "pod2usage()" to print usage messages for
+a Perl script based on its embedded pod documentation. The pod2usage()
+function is generally useful to all script authors since it lets them
+write and maintain a single source (the pods) for documentation, thus
+removing the need to create and maintain redundant usage message text
+consisting of information already in the pods.
-=head2 pack() format modifier '!' supported
+There is also a pod2usage script which can be used from other kinds of
+scripts to print usage messages from pods (even for non-Perl scripts
+with pods embedded in comments).
-The new format type modifier '!' is useful for packing and unpacking
-native shorts, ints, and longs. See L<perlfunc/"pack">.
+For details and examples, please see L<Pod::Usage>.
-=head2 pack() and unpack() support counted strings
+=item Pod::Text and Pod::Man
-The template character '/' can be used to specify a counted string
-type to be packed or unpacked. See L<perlfunc/"pack">.
+Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
+still available for backwards compatibility, the module now has a new
+preferred interface. See L<Pod::Text> for the details. The new Pod::Text
+module is easily subclassed for tweaks to the output, and two such
+subclasses (Pod::Text::Termcap for man-page-style bold and underlining
+using termcap information, and Pod::Text::Color for markup with ANSI color
+sequences) are now standard.
-=head2 Comments in pack() templates
+pod2man has been turned into a module, Pod::Man, which also uses
+Pod::Parser. In the process, several outstanding bugs related to quotes
+in section headers, quoting of code escapes, and nested lists have been
+fixed. pod2man is now a wrapper script around this module.
-The '#' character in a template introduces a comment up to
-end of the line. This facilitates documentation of pack()
-templates.
+=item SDBM_File
-=head2 $^X variables may now have names longer than one character
+An EXISTS method has been added to this module (and sdbm_exists() has
+been added to the underlying sdbm library), so one can now call exists
+on an SDBM_File tied hash and get the correct result, rather than a
+runtime error.
-Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
-error. Now variable names that begin with a control character may be
-arbitrarily long. However, for compatibility reasons, these variables
-I<must> be written with explicit braces, as C<${^XY}> for example.
-C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
-than one control character, such as C<${^XY^Z}>, are illegal.
+A bug that may have caused data loss when more than one disk block
+happens to be read from the database in a single FETCH() has been
+fixed.
-The old syntax has not changed. As before, `^X' may be either a
-literal control-X character or the two-character sequence `caret' plus
-`X'. When braces are omitted, the variable name stops after the
-control character. Thus C<"$^XYZ"> continues to be synonymous with
-C<$^X . "YZ"> as before.
+=item Sys::Syslog
-As before, lexical variables may not have names beginning with control
-characters. As before, variables whose names begin with a control
-character are always forced to be in package `main'. All such variables
-are reserved for future extensions, except those that begin with
-C<^_>, which may be used by user programs and are guaranteed not to
-acquire special meaning in any future version of Perl.
+Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
+no longer requires syslog.ph to exist.
-=head2 C<use attrs> implicit in subroutine attributes
+=item Sys::Hostname
-Formerly, if you wanted to mark a subroutine as being a method call or
-as requiring an automatic lock() when it is entered, you had to declare
-that with a C<use attrs> pragma in the body of the subroutine.
-That can now be accomplished with declaration syntax, like this:
+Sys::Hostname now uses XSUBs to call the C library's gethostname() or
+uname() if they exist.
- sub mymethod : locked method ;
- ...
- sub mymethod : locked method {
- ...
- }
+=item Term::ANSIColor
- sub othermethod :locked :method ;
- ...
- sub othermethod :locked :method {
- ...
- }
+Term::ANSIColor is a very simple module to provide easy and readable
+access to the ANSI color and highlighting escape sequences, supported by
+most ANSI terminal emulators. It is now included standard.
+=item Time::Local
-(Note how only the first C<:> is mandatory, and whitespace surrounding
-the C<:> is optional.)
+The timelocal() and timegm() functions used to silently return bogus
+results when the date fell outside the machine's integer range. They
+now consistently croak() if the date falls in an unsupported range.
-F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
-with the stubs they provide. See L<attributes>.
+=item Win32
-=head2 Regular expression improvements
+The error return value in list context has been changed for all functions
+that return a list of values. Previously these functions returned a list
+with a single element C<undef> if an error occurred. Now these functions
+return the empty list in these situations. This applies to the following
+functions:
-change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+ Win32::FsType
+ Win32::GetOSVersion
-=head2 Overloading improvements
+The remaining functions are unchanged and continue to return C<undef> on
+error even in list context.
-change#2150
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+The Win32::SetLastError(ERROR) function has been added as a complement
+to the Win32::GetLastError() function.
-=head2 open() with more than two arguments
+The new Win32::GetFullPathName(FILENAME) returns the full absolute
+pathname for FILENAME in scalar context. In list context it returns
+a two-element list containing the fully qualified directory name and
+the filename. See L<Win32>.
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+=item XSLoader
-=head2 Support for interpolating named characters
+The XSLoader extension is a simpler alternative to DynaLoader.
+See L<XSLoader>.
-change#4052
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+=item DBM Filters
-=head2 Experimental support for user-hooks in @INC
+A new feature called "DBM Filters" has been added to all the
+DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
+DBM Filters add four new methods to each DBM module:
-[TODO - Ken Fox <kfox@ford.com>]
+ filter_store_key
+ filter_store_value
+ filter_fetch_key
+ filter_fetch_value
-=head2 C<require> and C<do> may be overridden
+These can be used to filter key-value pairs before the pairs are
+written to the database or just after they are read from the database.
+See L<perldbmfilter> for further information.
-C<require> and C<do 'file'> operations may be overridden locally
-by importing subroutines of the same name into the current package
-(or globally by importing them into the CORE::GLOBAL:: namespace).
-Overriding C<require> will also affect C<use>, provided the override
-is visible at compile-time.
-See L<perlsub/"Overriding Built-in Functions">.
+=back
-=head2 New variable $^C reflects C<-c> switch
+=head2 Pragmata
-C<$^C> has a boolean value that reflects whether perl is being run
-in compile-only mode (i.e. via the C<-c> switch). Since
-BEGIN blocks are executed under such conditions, this variable
-enables perl code to determine whether actions that make sense
-only during normal running are warranted. See L<perlvar>.
+C<use attrs> is now obsolete, and is only provided for
+backward-compatibility. It's been replaced by the C<sub : attributes>
+syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
-=head2 New variable $^V contains Perl version in v5.6.0 format
+Lexical warnings pragma, C<use warnings;>, to control optional warnings.
+See L<perllexwarn>.
-C<$^V> contains the Perl version number as a string composed of
-characters whose ordinals match the version numbers, so that it may
-be used in string comparisons.
+C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
+...). Currently only one subpragma implemented, "use filetest
+'access';", that uses access(2) or equivalent to check permissions
+instead of using stat(2) as usual. This matters in filesystems
+where there are ACLs (access control lists): the stat(2) might lie,
+but access(2) knows better.
-See C<Support for strings represented as a vector of ordinals> for an
-example.
+The C<open> pragma can be used to specify default disciplines for
+handle constructors (e.g. open()) and for qx//. The two
+pseudo-disciplines C<:raw> and C<:crlf> are currently supported on
+DOS-derivative platforms (i.e. where binmode is not a no-op).
+See also L</"binmode() can be used to set :crlf and :raw modes">.
-=head2 Optional Y2K warnings
+=head1 Utility Changes
-If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
-it emits optional warnings when concatenating the number 19
-with another number.
+=head2 dprofpp
-This behavior must be specifically enabled when running Configure.
-See F<INSTALL> and F<README.Y2K>.
+C<dprofpp> is used to display profile data generated using C<Devel::DProf>.
+See L<dprofpp>.
-=head1 Significant bug fixes
+=head2 find2perl
-=head2 E<lt>HANDLEE<gt> on empty files
+The C<find2perl> utility now uses the enhanced features of the File::Find
+module. The -depth and -follow options are supported. Pod documentation
+is also included in the script.
-With C<$/> set to C<undef>, "slurping" an empty file returns a string of
-zero length (instead of C<undef>, as it used to) the first time the
-HANDLE is read after C<$/> is set to C<undef>. Further reads yield
-C<undef>.
+=head2 h2xs
-This means that the following will append "foo" to an empty file (it used
-to do nothing):
+The C<h2xs> tool can now work in conjunction with C<C::Scan> (available
+from CPAN) to automatically parse real-life header files. The C<-M>,
+C<-a>, C<-k>, and C<-o> options are new.
- perl -0777 -pi -e 's/^/foo/' empty_file
+=head2 perlcc
-The behaviour of:
+C<perlcc> now supports the C and Bytecode backends. By default,
+it generates output from the simple C backend rather than the
+optimized C backend.
- perl -pi -e 's/^/foo/' empty_file
+Support for non-Unix platforms has been improved.
-is unchanged (it continues to leave the file empty).
+=head2 perldoc
-=head2 C<eval '...'> improvements
+C<perldoc> has been reworked to avoid possible security holes.
+It will not by default let itself be run as the superuser, but you
+may still use the B<-U> switch to try to make it drop privileges
+first.
-Line numbers (as reflected by caller() and most diagnostics) within
-C<eval '...'> were often incorrect when here documents were involved.
-This has been corrected.
+=head2 The Perl Debugger
-Lexical lookups for variables appearing in C<eval '...'> within
-functions that were themselves called within an C<eval '...'> were
-searching the wrong place for lexicals. The lexical search now
-correctly ends at the subroutine's block boundary.
+Many bug fixes and enhancements were added to F<perl5db.pl>, the
+Perl debugger. The help documentation was rearranged. New commands
+include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current
+actions, C<man I<docpage>> to run your doc viewer on some perl
+docset, and support for quoted options. The help information was
+rearranged, and should be viewable once again if you're using B<less>
+as your pager. A serious security hole was plugged--you should
+immediately remove all older versions of the Perl debugger as
+installed in previous releases, all the way back to perl3, from
+your system to avoid being bitten by this.
-Parsing of here documents used to be flawed when they appeared as
-the replacement expression in C<eval 's/.../.../e'>. This has
-been fixed.
+=head1 Improved Documentation
-=head2 All compilation errors are true errors
+Many of the platform-specific README files are now part of the perl
+installation. See L<perl> for the complete list.
-Some "errors" encountered at compile time were by neccessity
-generated as warnings followed by eventual termination of the
-program. This enabled more such errors to be reported in a
-single run, rather than causing a hard stop at the first error
-that was encountered.
+=over 4
-The mechanism for reporting such errors has been reimplemented
-to queue compile-time errors and report them at the end of the
-compilation as true errors rather than as warnings. This fixes
-cases where error messages leaked through in the form of warnings
-when code was compiled at run time using C<eval STRING>, and
-also allows such errors to be reliably trapped using __DIE__ hooks.
+=item perlapi.pod
-=head2 Automatic flushing of output buffers
+The official list of public Perl API functions.
-fork(), exec(), system(), qx//, and pipe open()s now flush buffers
-of all files opened for output when the operation
-was attempted. This mostly eliminates confusing
-buffering mishaps suffered by users unaware of how Perl internally
-handles I/O.
+=item perlboot.pod
-=head2 Better diagnostics on meaningless filehandle operations
+A tutorial for beginners on object-oriented Perl.
-Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
-are compile time errors. Attempting to read from filehandles that
-were opened only for writing will now produce warnings (just as
-writing to read-only filehandles does).
+=item perlcompile.pod
-=head2 Where possible, buffered data discarded from duped input filehandle
+An introduction to using the Perl Compiler suite.
-C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
-was previously read and buffered in C<OLD> before duping the handle.
-On platforms where doing this is allowed, the next read operation
-on C<NEW> will return the same data as the corresponding operation
-on C<OLD>. Formerly, it would have returned the data from the start
-of the following disk block instead.
+=item perldbmfilter.pod
-=head2 eof() has the same old magic as <>
+A howto document on using the DBM filter facility.
-C<eof()> would return true if no attempt to read from C<E<lt>E<gt>> had
-yet been made. C<eof()> has been changed to have a little magic of its
-own, it now opens the C<E<lt>E<gt>> files.
+=item perldebug.pod
-=head2 system(), backticks and pipe open now reflect exec() failure
+All material unrelated to running the Perl debugger, plus all
+low-level guts-like details that risked crushing the casual user
+of the debugger, have been relocated from the old manpage to the
+next entry below.
-On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
-etc., are implemented via fork() and exec(). When the underlying
-exec() fails, earlier versions did not report the error properly,
-since the exec() happened to be in a different process.
+=item perldebguts.pod
-The child process now communicates with the parent about the
-error in launching the external command, which allows these
-constructs to return with their usual error value and set $!.
+This new manpage contains excessively low-level material not related
+to the Perl debugger, but slightly related to debugging Perl itself.
+It also contains some arcane internal details of how the debugging
+process works that may only be of interest to developers of Perl
+debuggers.
-=head2 Implicitly closed filehandles are safer
+=item perlfork.pod
-Sometimes implicitly closed filehandles (as when they are localized,
-and Perl automatically closes them on exiting the scope) could
-inadvertently set $? or $!. This has been corrected.
+Notes on the fork() emulation currently available for the Windows platform.
-=head2 C<(\$)> prototype and C<$foo{a}>
+=item perlfilter.pod
-An scalar reference prototype now correctly allows a hash or
-array element in that slot.
+An introduction to writing Perl source filters.
-=head2 Pseudo-hashes work better
+=item perlhack.pod
-Dereferencing some types of reference values in a pseudo-hash,
-such as C<$ph-E<gt>{foo}[1]>, was accidentally disallowed. This has
-been corrected.
+Some guidelines for hacking the Perl source code.
-When applied to a pseudo-hash element, exists() now reports whether
-the specified value exists, not merely if the key is valid.
+=item perlintern.pod
-delete() now works on pseudo-hashes. When given a pseudo-hash element
-or slice it deletes the values corresponding to the keys (but not the keys
-themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
+A list of internal functions in the Perl source code.
+(List is currently empty.)
-Pseudo-hash slices with constant keys are now optimized to array lookups
-at compile-time.
+=item perllexwarn.pod
-The C<fields> pragma now provides ways to create pseudo-hashes, via
-fields::new() and fields::phash(). See L<fields>.
+Introduction and reference information about lexically scoped
+warning categories.
-=head2 C<goto &sub> and AUTOLOAD
+=item perlnumber.pod
-The C<goto &sub> construct works correctly when C<&sub> happens
-to be autoloaded.
+Detailed information about numbers as they are represented in Perl.
-=head2 C<-bareword> allowed under C<use integer>
+=item perlopentut.pod
-The autoquoting of barewords preceded by C<-> did not work
-in prior versions when the C<integer> pragma was enabled.
-This has been fixed.
+A tutorial on using open() effectively.
-=head2 Boolean assignment operators are legal lvalues
+=item perlreftut.pod
-Constructs such as C<($a ||= 2) += 1> are now allowed.
+A tutorial that introduces the essentials of references.
-=head2 C<sort $coderef @foo> allowed
+=item perltootc.pod
-sort() did not accept a subroutine reference as the comparison
-function in earlier versions. This is now permitted.
+A tutorial on managing class data for object modules.
-=head2 Failures in DESTROY()
+=item perltodo.pod
-When code in a destructor threw an exception, it went unnoticed
-in earlier versions of Perl, unless someone happened to be
-looking in $@ just after the point the destructor happened to
-run. Such failures are now visible as warnings when warnings are
-enabled.
+Discussion of the most often wanted features that may someday be
+supported in Perl.
-=head2 Locale bugs fixed
+=item perlunicode.pod
-printf() and sprintf() previously reset the numeric locale
-back to the default "C" locale. This has been fixed.
+An introduction to Unicode support features in Perl.
-Numbers formatted according to the local numeric locale
-(such as using a decimal comma instead of a decimal dot) caused
-"isn't numeric" warnings, even while the operations accessing
-those numbers produced correct results. The warnings are gone.
+=back
-=head2 Memory leaks
+=head1 Performance enhancements
-The C<eval 'return sub {...}'> construct could sometimes leak
-memory. This has been fixed.
+=head2 Simple sort() using { $a <=> $b } and the like are optimized
-Operations that aren't filehandle constructors used to leak memory
-when used on invalid filehandles. This has been fixed.
+Many common sort() operations using a simple inlined block are now
+optimized for faster performance.
-Constructs that modified C<@_> could fail to deallocate values
-in C<@_> and thus leak memory. This has been corrected.
+=head2 Optimized assignments to lexical variables
-=head2 Spurious subroutine stubs after failed subroutine calls
+Certain operations in the RHS of assignment statements have been
+optimized to directly set the lexical variable on the LHS,
+eliminating redundant copying overheads.
-Perl could sometimes create empty subroutine stubs when a
-subroutine was not found in the package. Such cases stopped
-later method lookups from progressing into base packages.
-This has been corrected.
+=head2 Faster subroutine calls
-=head2 Consistent numeric conversions
+Minor changes in how subroutine calls are handled internally
+provide marginal improvements in performance.
-change#3378,3318
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+=item delete(), each(), values() and hash iteration are faster
-=head2 Taint failures under C<-U>
+The hash values returned by delete(), each(), values() and hashes in a
+list context are the actual values in the hash, instead of copies.
+This results in significantly better performance, because it eliminates
+needless copying in most situations.
-When running in unsafe mode, taint violations could sometimes
-cause silent failures. This has been fixed.
+=head1 Installation and Configuration Improvements
-=head2 END blocks and the C<-c> switch
+=head2 -Dusethreads means something different
-Prior versions used to run BEGIN B<and> END blocks when Perl was
-run in compile-only mode. Since this is typically not the expected
-behavior, END blocks are not executed anymore when the C<-c> switch
-is used.
+The -Dusethreads flag now enables the experimental interpreter-based thread
+support by default. To get the flavor of experimental threads that was in
+5.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
-See L<CHECK blocks> for how to run things when the compile phase ends.
+As of v5.6.0, interpreter-threads support is still lacking a way to
+create new threads from Perl (i.e., C<use Thread;> will not work with
+interpreter threads). C<use Thread;> continues to be available when you
+specify the -Duse5005threads option to Configure, bugs and all.
-=head2 Potential to leak DATA filehandles
+ NOTE: Support for threads continues to be an experimental feature.
+ Interfaces and implementation are subject to sudden and drastic changes.
-Using the C<__DATA__> token creates an implicit filehandle to
-the file that contains the token. It is the program's
-responsibility to close it when it is done reading from it.
+=head2 New Configure flags
-This caveat is now better explained in the documentation.
-See L<perldata>.
+The following new flags may be enabled on the Configure command line
+by running Configure with C<-Dflag>.
-=head2 Diagnostics follow STDERR
+ usemultiplicity
+ usethreads useithreads (new interpreter threads: no Perl API yet)
+ usethreads use5005threads (threads as they were in 5.005)
-Diagnostic output now goes to whichever file the C<STDERR> handle
-is pointing at, instead of always going to the underlying C runtime
-library's C<stderr>.
+ use64bitint (equal to now deprecated 'use64bits')
+ use64bitall
-=head2 Other fixes for better diagnostics
+ uselongdouble
+ usemorebits
+ uselargefiles
+ usesocks (only SOCKS v5 supported)
-Line numbers are no longer suppressed (under most likely circumstances)
-during the global destruction phase.
+=head2 Threadedness and 64-bitness now more daring
-Diagnostics emitted from code running in threads other than the main
-thread are now accompanied by the thread ID.
+The Configure options enabling the use of threads and the use of
+64-bitness are now more daring in the sense that they no more have an
+explicit list of operating systems of known threads/64-bit
+capabilities. In other words: if your operating system has the
+necessary APIs and datatypes, you should be able just to go ahead and
+use them, for threads by Configure -Dusethreads, and for 64 bits
+either explicitly by Configure -Duse64bitint or implicitly if your
+system has 64-bit wide datatypes. See also L<"64-bit support">.
-Embedded null characters in diagnostics now actually show up. They
-used to truncate the message in prior versions.
+=head2 Long Doubles
-$foo::a and $foo::b are now exempt from "possible typo" warnings only
-if sort() is encountered in package foo.
+Some platforms have "long doubles", floating point numbers of even
+larger range than ordinary "doubles". To enable using long doubles for
+Perl's scalars, use -Duselongdouble.
-Unrecognized alphabetic escapes encountered when parsing quote
-constructs now generate a warning, since they may take on new
-semantics in later versions of Perl.
+=head2 -Dusemorebits
-=head1 Performance enhancements
+You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
+See also L<"64-bit support">.
-=head2 Simple sort() using { $a <=> $b } and the like are optimized
+=head2 -Duselargefiles
-Many common sort() operations using a simple inlined block are now
-optimized for faster performance.
+Some platforms support system APIs that are capable of handling large files
+(typically, files larger than two gigabytes). Perl will try to use these
+APIs if you ask for -Duselargefiles.
-=head2 Optimized assignments to lexical variables
+See L<"Large file support"> for more information.
-Certain operations in the RHS of assignment statements have been
-optimized to directly set the lexical variable on the LHS,
-eliminating redundant copying overheads.
+=head2 installusrbinperl
+
+You can use "Configure -Uinstallusrbinperl" which causes installperl
+to skip installing perl also as /usr/bin/perl. This is useful if you
+prefer not to modify /usr/bin for some reason or another but harmful
+because many scripts assume to find Perl in /usr/bin/perl.
-=head2 Method lookups optimized
+=head2 SOCKS support
-[TODO - Chip Salzenberg <chip@perlsupport.com>]
+You can use "Configure -Dusesocks" which causes Perl to probe
+for the SOCKS proxy protocol library (v5, not v4). For more information
+on SOCKS, see:
-=head2 Faster mechanism to invoke XSUBs
+ http://www.socks.nec.com/
-change#4044,4125
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+=head2 C<-A> flag
-=head2 Perl_malloc() improvements
+You can "post-edit" the Configure variables using the Configure C<-A>
+switch. The editing happens immediately after the platform specific
+hints files have been processed but before the actual configuration
+process starts. Run C<Configure -h> to find out the full C<-A> syntax.
-change#4237
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+=head2 Enhanced Installation Directories
-=head2 Faster subroutine calls
+The installation structure has been enriched to improve the support
+for maintaining multiple versions of perl, to provide locations for
+vendor-supplied modules, scripts, and manpages, and to ease maintenance
+of locally-added modules, scripts, and manpages. See the section on
+Installation Directories in the INSTALL file for complete details.
+For most users building and installing from source, the defaults should
+be fine.
-Minor changes in how subroutine calls are handled internally
-provide marginal improvements in performance.
+If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
+special values for library directories, you might wish to consider using
+the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
+config.sh file from an earlier version of perl, you should be sure to
+check that Configure makes sensible choices for the new directories.
+See INSTALL for complete details.
=head1 Platform specific changes
-=head2 Additional supported platforms
+=head2 Supported platforms
=over 4
=item *
-Rhapsody is now supported.
+Rhapsody/Darwin is now supported.
=item *
EPOC is is now supported (on Psion 5).
+=item *
+
+The cygwin port (formerly cygwin32) has been greatly improved.
+
=back
=head2 DOS
=item *
-Wrong exit code from backticks now fixed.
+Incorrect exit codes from backticks have been fixed.
=item *
-This port is still using its own builtin globbing.
+This port continues to use its own builtin globbing (not File::Glob).
=back
-=head2 OS/2
+=head2 OS390 (OpenEdition MVS)
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+Support for this EBCDIC platform has not been renewed in this release.
+There are difficulties in reconciling Perl's standardization on UTF-8
+as its internal representation for characters with the EBCDIC character
+set, because the two are incompatible.
+
+It is unclear whether future versions will renew support for this
+platform, but the possibility exists.
=head2 VMS
-[TODO - Charles Bailey <bailey@newman.upenn.edu>]
+Numerous revisions and extensions to configuration, build, testing, and
+installation process to accomodate core changes and VMS-specific options.
+
+Expand %ENV-handling code to allow runtime mapping to logical names,
+CLI symbols, and CRTL environ array.
+
+Extension of subprocess invocation code to accept filespecs as command
+"verbs".
+
+Add to Perl command line processing the ability to use default file types and
+to recognize Unix-style C<2E<gt>&1>.
+
+Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.
+
+Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.
+
+Barewords at start of Unix-syntax paths may be treated as text rather than
+only as logical names.
+
+Optional secure translation of several logical names used internally by Perl.
+
+Miscellaneous bugfixing and porting of new core code to VMS.
+
+Thanks are gladly extended to the many people who have contributed VMS
+patches, testing, and ideas.
=head2 Win32
-Site library searches failed to look for ".../site/5.XXX/lib"
-if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
+Perl can now emulate fork() internally, using multiple interpreters running
+in different concurrent threads. This support must be enabled at build
+time. See L<perlfork> for detailed information.
-When given a pathname that consists only of a drivename, such
-as C<A:>, opendir() and stat() now use the current working
-directory for the drive rather than the drive root.
+When given a pathname that consists only of a drivename, such as C<A:>,
+opendir() and stat() now use the current working directory for the drive
+rather than the drive root.
-The builtin XSUB functions in the Win32:: namespace are
-documented. See L<Win32>.
+The builtin XSUB functions in the Win32:: namespace are documented. See
+L<Win32>.
$^X now contains the full path name of the running executable.
The C<Shell> module is supported.
-Rudimentary support for building under command.com in Windows 95
+Better support for building Perl under command.com in Windows 95
has been added.
Scripts are read in binary mode by default to allow ByteLoader (and
which supports glob syntax of the C shell. This increases the flexibility
of the glob() operator, but there may be compatibility issues for
programs that relied on the older globbing syntax. If you want to
-preserve compatibility with the older syntax, you might want to put
-a C<use File::DosGlob;> in your program. For details and compatibility
-information, see L<File::Glob>.
+preserve compatibility with the older syntax, you might want to run
+perl with C<-MFile::DosGlob>. For details and compatibility information,
+see L<File::Glob>.
-[TODO - GSAR]
-
-=head1 New tests
+=head1 Significant bug fixes
-=over 4
+=head2 <HANDLE> on empty files
-=item lib/attrs
+With C<$/> set to C<undef>, "slurping" an empty file returns a string of
+zero length (instead of C<undef>, as it used to) the first time the
+HANDLE is read after C<$/> is set to C<undef>. Further reads yield
+C<undef>.
-Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
+This means that the following will append "foo" to an empty file (it used
+to do nothing):
-=item lib/env
+ perl -0777 -pi -e 's/^/foo/' empty_file
-Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
+The behaviour of:
-=item lib/env-array
+ perl -pi -e 's/^/foo/' empty_file
-Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
+is unchanged (it continues to leave the file empty).
-=item lib/io_const
+=head2 C<eval '...'> improvements
-IO constants (SEEK_*, _IO*).
+Line numbers (as reflected by caller() and most diagnostics) within
+C<eval '...'> were often incorrect where here documents were involved.
+This has been corrected.
-=item lib/io_dir
+Lexical lookups for variables appearing in C<eval '...'> within
+functions that were themselves called within an C<eval '...'> were
+searching the wrong place for lexicals. The lexical search now
+correctly ends at the subroutine's block boundary.
-Directory-related IO methods (new, read, close, rewind, tied delete).
+The use of C<return> within C<eval {...}> caused $@ not to be reset
+correctly when no exception occurred within the eval. This has
+been fixed.
-=item lib/io_multihomed
+Parsing of here documents used to be flawed when they appeared as
+the replacement expression in C<eval 's/.../.../e'>. This has
+been fixed.
-INET sockets with multi-homed hosts.
+=head2 All compilation errors are true errors
-=item lib/io_poll
+Some "errors" encountered at compile time were by neccessity
+generated as warnings followed by eventual termination of the
+program. This enabled more such errors to be reported in a
+single run, rather than causing a hard stop at the first error
+that was encountered.
-IO poll().
+The mechanism for reporting such errors has been reimplemented
+to queue compile-time errors and report them at the end of the
+compilation as true errors rather than as warnings. This fixes
+cases where error messages leaked through in the form of warnings
+when code was compiled at run time using C<eval STRING>, and
+also allows such errors to be reliably trapped using C<eval "...">.
-=item lib/io_unix
+=head2 Implicitly closed filehandles are safer
-UNIX sockets.
+Sometimes implicitly closed filehandles (as when they are localized,
+and Perl automatically closes them on exiting the scope) could
+inadvertently set $? or $!. This has been corrected.
-=item op/attrs
-Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
+=head2 Behavior of list slices is more consistent
-=item op/filetest
+When taking a slice of a literal list (as opposed to a slice of
+an array or hash), Perl used to return an empty list if the
+result happened to be composed of all undef values.
-File test operators.
+The new behavior is to produce an empty list if (and only if)
+the original list was empty. Consider the following example:
-=item op/lex_assign
+ @a = (1,undef,undef,2)[2,1,2];
-Verify operations that access pad objects (lexicals and temporaries).
+The old behavior would have resulted in @a having no elements.
+The new behavior ensures it has three undefined elements.
-=item op/exists_sub
+Note in particular that the behavior of slices of the following
+cases remains unchanged:
-Verify C<exists &sub> operations.
+ @a = ()[1,2];
+ @a = (getpwent)[7,0];
+ @a = (anything_returning_empty_list())[2,1,2];
+ @a = @b[2,1,2];
+ @a = @c{'a','b','c'};
-=back
+See L<perldata>.
-=head1 Modules and Pragmata
+=head2 C<(\$)> prototype and C<$foo{a}>
-=head2 Modules
+A scalar reference prototype now correctly allows a hash or
+array element in that slot.
-=over 4
+=head2 C<goto &sub> and AUTOLOAD
-=item attributes
+The C<goto &sub> construct works correctly when C<&sub> happens
+to be autoloaded.
-While used internally by Perl as a pragma, this module also
-provides a way to fetch subroutine and variable attributes.
-See L<attributes>.
+=head2 C<-bareword> allowed under C<use integer>
-=item B
+The autoquoting of barewords preceded by C<-> did not work
+in prior versions when the C<integer> pragma was enabled.
+This has been fixed.
-The Perl Compiler suite has been extensively reworked for this
-release.
+=head2 Failures in DESTROY()
-[TODO - Vishal Bhatia <vishal@gol.com>,
-Nick Ing-Simmons <nick@ni-s.u-net.com>]
+When code in a destructor threw an exception, it went unnoticed
+in earlier versions of Perl, unless someone happened to be
+looking in $@ just after the point the destructor happened to
+run. Such failures are now visible as warnings when warnings are
+enabled.
-=item ByteLoader
+=head2 Locale bugs fixed
-The ByteLoader is a dedicated extension to generate and run
-Perl bytecode. See L<ByteLoader>.
+printf() and sprintf() previously reset the numeric locale
+back to the default "C" locale. This has been fixed.
-=item constant
+Numbers formatted according to the local numeric locale
+(such as using a decimal comma instead of a decimal dot) caused
+"isn't numeric" warnings, even while the operations accessing
+those numbers produced correct results. These warnings have been
+discontinued.
-References can now be used.
+=head2 Memory leaks
-The new version also allows a leading underscore in constant names, but
-disallows a double leading underscore (as in "__LINE__"). Some other names
-are disallowed or warned against, including BEGIN, END, etc. Some names
-which were forced into main:: used to fail silently in some cases; now they're
-fatal (outside of main::) and an optional warning (inside of main::).
-The ability to detect whether a constant had been set with a given name has
-been added.
+The C<eval 'return sub {...}'> construct could sometimes leak
+memory. This has been fixed.
-See L<constant>.
+Operations that aren't filehandle constructors used to leak memory
+when used on invalid filehandles. This has been fixed.
-=item charnames
+Constructs that modified C<@_> could fail to deallocate values
+in C<@_> and thus leak memory. This has been corrected.
-change#4052
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+=head2 Spurious subroutine stubs after failed subroutine calls
-=item Data::Dumper
+Perl could sometimes create empty subroutine stubs when a
+subroutine was not found in the package. Such cases stopped
+later method lookups from progressing into base packages.
+This has been corrected.
-A C<Maxdepth> setting can be specified to avoid venturing
-too deeply into deep data structures. See L<Data::Dumper>.
+=head2 Taint failures under C<-U>
-Dumping C<qr//> objects works correctly.
+When running in unsafe mode, taint violations could sometimes
+cause silent failures. This has been fixed.
-=item DB
+=head2 END blocks and the C<-c> switch
-C<DB> is an experimental module that exposes a clean abstraction
-to Perl's debugging API.
+Prior versions used to run BEGIN B<and> END blocks when Perl was
+run in compile-only mode. Since this is typically not the expected
+behavior, END blocks are not executed anymore when the C<-c> switch
+is used.
-=item DB_File
+See L<CHECK blocks> for how to run things when the compile phase ends.
-DB_File can now be built with Berkeley DB versions 1, 2 or 3.
-See C<ext/DB_File/Changes>.
+=head2 Potential to leak DATA filehandles
-=item Devel::DProf
+Using the C<__DATA__> token creates an implicit filehandle to
+the file that contains the token. It is the program's
+responsibility to close it when it is done reading from it.
-Devel::DProf, a Perl source code profiler has been added. See
-L<Devel::DProf> and L<dprofpp>.
+This caveat is now better explained in the documentation.
+See L<perldata>.
-=item Dumpvalue
+=head1 New or Changed Diagnostics
-The Dumpvalue module provides screen dumps of Perl data.
+=over 4
-=item Benchmark
+=item "%s" variable %s masks earlier declaration in same %s
-Overall, Benchmark results exhibit lower average error and better timing
-accuracy.
+(W misc) A "my" or "our" variable has been redeclared in the current scope or statement,
+effectively eliminating all access to the previous instance. This is almost
+always a typographical error. Note that the earlier variable will still exist
+until the end of the scope or until all closure referents to it are
+destroyed.
-You can now run tests for I<n> seconds instead of guessing the right
-number of tests to run: e.g. timethese(-5, ...) will run each
-code for at least 5 CPU seconds. Zero as the "number of repetitions"
-means "for at least 3 CPU seconds". The output format has also
-changed. For example:
+=item "my sub" not yet implemented
- use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
+(F) Lexically scoped subroutines are not yet implemented. Don't try that
+yet.
-will now output something like this:
+=item "our" variable %s redeclared
- Benchmark: running a, b, each for at least 5 CPU seconds...
- a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
- b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
+(W misc) You seem to have already declared the same global once before in the
+current lexical scope.
-New features: "each for at least N CPU seconds...", "wallclock secs",
-and the "@ operations/CPU second (n=operations)".
+=item '!' allowed only after types %s
-timethese() now returns a reference to a hash of Benchmark objects containing
-the test results, keyed on the names of the tests.
+(F) The '!' is allowed in pack() and unpack() only after certain types.
+See L<perlfunc/pack>.
-timethis() now returns the iterations field in the Benchmark result object
-instead of 0.
+=item / cannot take a count
-timethese(), timethis(), and the new cmpthese() (see below) can also take
-a format specifier of 'none' to suppress output.
+(F) You had an unpack template indicating a counted-length string,
+but you have also specified an explicit size for the string.
+See L<perlfunc/pack>.
-A new function countit() is just like timeit() except that it takes a
-TIME instead of a COUNT.
+=item / must be followed by a, A or Z
-A new function cmpthese() prints a chart comparing the results of each test
-returned from a timethese() call. For each possible pair of tests, the
-percentage speed difference (iters/sec or seconds/iter) is shown.
+(F) You had an unpack template indicating a counted-length string,
+which must be followed by one of the letters a, A or Z
+to indicate what sort of string is to be unpacked.
+See L<perlfunc/pack>.
-For other details, see L<Benchmark>.
+=item / must be followed by a*, A* or Z*
-=item Devel::Peek
+(F) You had a pack template indicating a counted-length string,
+Currently the only things that can have their length counted are a*, A* or Z*.
+See L<perlfunc/pack>.
-The Devel::Peek module provides access to the internal representation
-of Perl variables and data. It is a data debugging tool for the XS programmer.
+=item / must follow a numeric type
-=item English
+(F) You had an unpack template that contained a '#',
+but this did not follow some numeric unpack specification.
+See L<perlfunc/pack>.
-$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
-(a numeric value).
+=item /%s/: Unrecognized escape \\%c passed through
-=item Env
+(W regexp) You used a backslash-character combination which is not recognized
+by Perl. This combination appears in an interpolated variable or a
+C<'>-delimited regular expression. The character was understood literally.
-Env now supports accessing environment variables like PATH as array
-variables.
+=item /%s/: Unrecognized escape \\%c in character class passed through
-=item ExtUtils::MakeMaker
+(W regexp) You used a backslash-character combination which is not recognized
+by Perl inside character classes. The character was understood literally.
-change#4135, also needs docs in module pod
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+=item /%s/ should probably be written as "%s"
-=item Fcntl
+(W syntax) You have used a pattern where Perl expected to find a string,
+as in the first argument to C<join>. Perl will treat the true
+or false result of matching the pattern against $_ as the string,
+which is probably not what you had in mind.
-More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
-large file (more than 4GB) access Note that the O_LARGEFILE is
-automatically/transparently added to sysopen() flags if large file
-support has been configured), Free/Net/OpenBSD locking behaviour flags
-F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
-O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
-SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
-The chmod()/stat() S_IF* constants and S_IS* functions are available
-via the C<:mode> tag.
+=item %s() called too early to check prototype
+(W prototype) You've called a function that has a prototype before the parser saw a
+definition or declaration for it, and Perl could not check that the call
+conforms to the prototype. You need to either add an early prototype
+declaration for the subroutine in question, or move the subroutine
+definition ahead of the call to get proper prototype checking. Alternatively,
+if you are certain that you're calling the function correctly, you may put
+an ampersand before the name to avoid the warning. See L<perlsub>.
-=item File::Compare
+=item %s argument is not a HASH or ARRAY element
-A compare_text() function has been added, which allows custom
-comparison functions. See L<File::Compare>.
+(F) The argument to exists() must be a hash or array element, such as:
-=item File::Find
+ $foo{$bar}
+ $ref->{"susie"}[12]
-File::Find now works correctly when the wanted() function is either
-autoloaded or is a symbolic reference.
+=item %s argument is not a HASH or ARRAY element or slice
-A bug that caused File::Find to lose track of the working directory
-when pruning top-level directories has been fixed.
+(F) The argument to delete() must be either a hash or array element, such as:
-File::Find now also supports several other options to control its
-behavior. It can follow symbolic links if the C<follow> option is
-specified. Enabling the C<no_chdir> option will make File::Find skip
-changing the current directory when walking directories. The C<untaint>
-flag can be useful when running with taint checks enabled.
+ $foo{$bar}
+ $ref->{"susie"}[12]
-See L<File::Find>.
+or a hash or array slice, such as:
-=item File::Glob
+ @foo[$bar, $baz, $xyzzy]
+ @{$ref->[12]}{"susie", "queue"}
-This extension implements BSD-style file globbing. By default,
-it will also be used for the internal implementation of the glob()
-operator. See L<File::Glob>.
+=item %s argument is not a subroutine name
-=item File::Spec
+(F) The argument to exists() for C<exists &sub> must be a subroutine
+name, and not a subroutine call. C<exists &sub()> will generate this error.
-New methods have been added to the File::Spec module: devnull() returns
-the name of the null device (/dev/null on Unix) and tmpdir() the name of
-the temp directory (normally /tmp on Unix). There are now also methods
-to convert between absolute and relative filenames: abs2rel() and
-rel2abs(). For compatibility with operating systems that specify volume
-names in file paths, the splitpath(), splitdir(), and catdir() methods
-have been added.
+=item %s package attribute may clash with future reserved word: %s
-=item File::Spec::Functions
+(W reserved) A lowercase attribute name was used that had a package-specific handler.
+That name might have a meaning to Perl itself some day, even though it
+doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
+See L<attributes>.
-The new File::Spec::Functions modules provides a function interface
-to the File::Spec module. Allows shorthand
+=item (in cleanup) %s
- $fullname = catfile($dir1, $dir2, $file);
+(W misc) This prefix usually indicates that a DESTROY() method raised
+the indicated exception. Since destructors are usually called by
+the system at arbitrary points during execution, and often a vast
+number of times, the warning is issued only once for any number
+of failures that would otherwise result in the same message being
+repeated.
-instead of
+Failure of user callbacks dispatched using the C<G_KEEPERR> flag
+could also result in this warning. See L<perlcall/G_KEEPERR>.
- $fullname = File::Spec->catfile($dir1, $dir2, $file);
+=item <> should be quotes
-=item Getopt::Long
+(F) You wrote C<< require <file> >> when you should have written
+C<require 'file'>.
-Getopt::Long licensing has changed to allow the Perl Artistic License
-as well as the GPL. It used to be GPL only, which got in the way of
-non-GPL applications that wanted to use Getopt::Long.
+=item Attempt to join self
-Getopt::Long encourages the use of Pod::Usage to produce help
-messages. For example:
+(F) You tried to join a thread from within itself, which is an
+impossible task. You may be joining the wrong thread, or you may
+need to move the join() to some other thread.
- use Getopt::Long;
- use Pod::Usage;
- my $man = 0;
- my $help = 0;
- GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
- pod2usage(1) if $help;
- pod2usage(-exitstatus => 0, -verbose => 2) if $man;
+=item Bad evalled substitution pattern
- __END__
+(F) You've used the /e switch to evaluate the replacement for a
+substitution, but perl found a syntax error in the code to evaluate,
+most likely an unexpected right brace '}'.
- =head1 NAME
+=item Bad realloc() ignored
- sample - Using GetOpt::Long and Pod::Usage
+(S) An internal routine called realloc() on something that had never been
+malloc()ed in the first place. Mandatory, but can be disabled by
+setting environment variable C<PERL_BADFREE> to 1.
- =head1 SYNOPSIS
+=item Bareword found in conditional
- sample [options] [file ...]
+(W bareword) The compiler found a bareword where it expected a conditional,
+which often indicates that an || or && was parsed as part of the
+last argument of the previous construct, for example:
- Options:
- -help brief help message
- -man full documentation
+ open FOO || die;
- =head1 OPTIONS
+It may also indicate a misspelled constant that has been interpreted
+as a bareword:
- =over 8
+ use constant TYPO => 1;
+ if (TYOP) { print "foo" }
- =item B<-help>
+The C<strict> pragma is useful in avoiding such errors.
- Print a brief help message and exits.
+=item Binary number > 0b11111111111111111111111111111111 non-portable
- =item B<-man>
+(W portable) The binary number you specified is larger than 2**32-1
+(4294967295) and therefore non-portable between systems. See
+L<perlport> for more on portability concerns.
- Prints the manual page and exits.
+=item Bit vector size > 32 non-portable
- =back
+(W portable) Using bit vector sizes larger than 32 is non-portable.
- =head1 DESCRIPTION
+=item Buffer overflow in prime_env_iter: %s
- B<This program> will read the given input file(s) and do someting
- useful with the contents thereof.
+(W internal) A warning peculiar to VMS. While Perl was preparing to iterate over
+%ENV, it encountered a logical name or symbol definition which was too long,
+so it was truncated to the string shown.
- =cut
+=item Can't check filesystem of script "%s"
-See L<Pod::Usage> for details.
+(P) For some reason you can't check the filesystem of the script for nosuid.
-A bug that prevented the non-option call-back E<lt>E<gt> from being
-specified as the first argument has been fixed.
+=item Can't declare class for non-scalar %s in "%s"
-To specify the characters E<lt> and E<gt> as option starters, use
-E<gt>E<lt>. Note, however, that changing option starters is strongly
-deprecated.
+(S) Currently, only scalar variables can declared with a specific class
+qualifier in a "my" or "our" declaration. The semantics may be extended
+for other types of variables in future.
-=item IO
+=item Can't declare %s in "%s"
-write() and syswrite() will now accept a single-argument
-form of the call, for consistency with Perl's syswrite().
+(F) Only scalar, array, and hash variables may be declared as "my" or
+"our" variables. They must have ordinary identifiers as names.
-You can now create a TCP-based IO::Socket::INET without forcing
-a connect attempt. This allows you to configure its options
-(like making it non-blocking) and then call connect() manually.
+=item Can't ignore signal CHLD, forcing to default
-A bug that prevented the IO::Socket::protocol() accessor
-from ever returning the correct value has been corrected.
+(W signal) Perl has detected that it is being run with the SIGCHLD signal
+(sometimes known as SIGCLD) disabled. Since disabling this signal
+will interfere with proper determination of exit status of child
+processes, Perl has reset the signal to its default value.
+This situation typically indicates that the parent program under
+which Perl may be running (e.g., cron) is being very careless.
-IO::Socket::connect now uses non-blocking IO instead of alarm()
-to do connect timeouts.
+=item Can't modify non-lvalue subroutine call
-IO::Socket::accept now uses select() instead of alarm() for doing
-timeouts.
+(F) Subroutines meant to be used in lvalue context should be declared as
+such, see L<perlsub/"Lvalue subroutines">.
-IO::Socket::INET->new now sets $! correctly on failure. $@ is
-still set for backwards compatability.
+=item Can't read CRTL environ
-=item JPL
+(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
+from the CRTL's internal environment array and discovered the array was
+missing. You need to figure out where your CRTL misplaced its environ
+or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
-Java Perl Lingo is now distributed with Perl. See jpl/README
-for more information.
+=item Can't remove %s: %s, skipping file
-=item lib
+(S) You requested an inplace edit without creating a backup file. Perl
+was unable to remove the original file to replace it with the modified
+file. The file was left unmodified.
-C<use lib> now weeds out any trailing duplicate entries.
-C<no lib> removes all named entries.
+=item Can't return %s from lvalue subroutine
-=item Math::BigInt
+(F) Perl detected an attempt to return illegal lvalues (such
+as temporary or readonly values) from a subroutine used as an lvalue.
+This is not allowed.
-The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
-and C<~> are now supported on bigints.
+=item Can't weaken a nonreference
-=item Math::Complex
+(F) You attempted to weaken something that was not a reference. Only
+references can be weakened.
-The accessor methods Re, Im, arg, abs, rho, and theta can now also
-act as mutators (accessor $z->Re(), mutator $z->Re(3)).
+=item Character class [:%s:] unknown
-=item Math::Trig
+(F) The class in the character class [: :] syntax is unknown.
+See L<perlre>.
-A little bit of radial trigonometry (cylindrical and spherical),
-radial coordinate conversions, and the great circle distance were added.
+=item Character class syntax [%s] belongs inside character classes
-=item Pod::Parser, Pod::InputObjects
+(W unsafe) The character class constructs [: :], [= =], and [. .] go
+I<inside> character classes, the [] are part of the construct,
+for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
+are not currently implemented; they are simply placeholders for
+future extensions.
-Pod::Parser is a base class for parsing and selecting sections of
-pod documentation from an input stream. This module takes care of
-identifying pod paragraphs and commands in the input and hands off the
-parsed paragraphs and commands to user-defined methods which are free
-to interpret or translate them as they see fit.
+=item Constant is not %s reference
-Pod::InputObjects defines some input objects needed by Pod::Parser, and
-for advanced users of Pod::Parser that need more about a command besides
-its name and text.
+(F) A constant value (perhaps declared using the C<use constant> pragma)
+is being dereferenced, but it amounts to the wrong type of reference. The
+message indicates the type of reference that was expected. This usually
+indicates a syntax error in dereferencing the constant value.
+See L<perlsub/"Constant Functions"> and L<constant>.
-As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
-"base parser code" recommended for use by all pod2xxx translators.
-Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
-to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
-underway. For any questions or comments about pod parsing and translating
-issues and utilities, please use the pod-people@perl.org mailing list.
+=item constant(%s): %s
-For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
+(F) The parser found inconsistencies either while attempting to define an
+overloaded constant, or when trying to find the character name specified
+in the C<\N{...}> escape. Perhaps you forgot to load the corresponding
+C<overload> or C<charnames> pragma? See L<charnames> and L<overload>.
-=item Pod::Checker, podchecker
+=item CORE::%s is not a keyword
-This utility checks pod files for correct syntax, according to
-L<perlpod>. Obvious errors are flagged as such, while warnings are
-printed for mistakes that can be handled gracefully. The checklist is
-not complete yet. See L<Pod::Checker>.
+(F) The CORE:: namespace is reserved for Perl keywords.
-=item Pod::ParseUtils, Pod::Find
+=item defined(@array) is deprecated
-These modules provide a set of gizmos that are useful mainly for pod
-translators. L<Pod::Find|Pod::Find> traverses directory structures and
-returns found pod files, along with their canonical names (like
-C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
-B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
-(for parsing the contents of C<LE<gt>E<lt>> sequences) and B<Pod::Cache>
-(for caching information about pod files, e.g. link nodes).
+(D) defined() is not usually useful on arrays because it checks for an
+undefined I<scalar> value. If you want to see if the array is empty,
+just use C<if (@array) { # not empty }> for example.
-=item Pod::Select, podselect
+=item defined(%hash) is deprecated
-Pod::Select is a subclass of Pod::Parser which provides a function
-named "podselect()" to filter out user-specified sections of raw pod
-documentation from an input stream. podselect is a script that provides
-access to Pod::Select from other scripts to be used as a filter.
-See L<Pod::Select>.
+(D) defined() is not usually useful on hashes because it checks for an
+undefined I<scalar> value. If you want to see if the hash is empty,
+just use C<if (%hash) { # not empty }> for example.
-=item Pod::Usage, pod2usage
+=item Did not produce a valid header
-Pod::Usage provides the function "pod2usage()" to print usage messages for
-a Perl script based on its embedded pod documentation. The pod2usage()
-function is generally useful to all script authors since it lets them
-write and maintain a single source (the pods) for documentation, thus
-removing the need to create and maintain redundant usage message text
-consisting of information already in the pods.
+See Server error.
-There is also a pod2usage script which can be used from other kinds of
-scripts to print usage messages from pods (even for non-Perl scripts
-with pods embedded in comments).
+=item (Did you mean "local" instead of "our"?)
-For details and examples, please see L<Pod::Usage>.
+(W misc) Remember that "our" does not localize the declared global variable.
+You have declared it again in the same lexical scope, which seems superfluous.
-=item Pod::Text and Pod::Man
+=item Document contains no data
-[TODO - Russ Allbery <rra@stanford.edu>]
+See Server error.
-=item SDBM_File
+=item entering effective %s failed
-An EXISTS method has been added to this module (and sdbm_exists() has
-been added to the underlying sdbm library), so one can now call exists
-on an SDBM_File tied hash and get the correct result, rather than a
-runtime error.
+(F) While under the C<use filetest> pragma, switching the real and
+effective uids or gids failed.
-A bug that may have caused data loss when more than one disk block
-happens to be read from the database in a single FETCH() has been
-fixed.
+=item false [] range "%s" in regexp
-=item Sys::Syslog
+(W regexp) A character class range must start and end at a literal character, not
+another character class like C<\d> or C<[:alpha:]>. The "-" in your false
+range is interpreted as a literal "-". Consider quoting the "-", "\-".
+See L<perlre>.
-Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
-no longer requires syslog.ph to exist.
+=item Filehandle %s opened only for output
-=item Sys::Hostname
+(W io) You tried to read from a filehandle opened only for writing. If you
+intended it to be a read/write filehandle, you needed to open it with
+"+<" or "+>" or "+>>" instead of with "<" or nothing. If
+you intended only to read from the file, use "<". See
+L<perlfunc/open>.
-Sys::Hostname now uses XSUBs to call the C library's gethostname() or
-uname() if they exist.
+=item flock() on closed filehandle %s
-=item Time::Local
+(W closed) The filehandle you're attempting to flock() got itself closed some
+time before now. Check your logic flow. flock() operates on filehandles.
+Are you attempting to call flock() on a dirhandle by the same name?
-The timelocal() and timegm() functions used to silently return bogus
-results when the date fell outside the machine's integer range. They
-now consistently croak() if the date falls in an unsupported range.
+=item Global symbol "%s" requires explicit package name
-=item Win32
+(F) You've said "use strict vars", which indicates that all variables
+must either be lexically scoped (using "my"), declared beforehand using
+"our", or explicitly qualified to say which package the global variable
+is in (using "::").
-The error return value in list context has been changed for all functions
-that return a list of values. Previously these functions returned a list
-with a single element C<undef> if an error occurred. Now these functions
-return the empty list in these situations. This applies to the following
-functions:
+=item Hexadecimal number > 0xffffffff non-portable
- Win32::FsType
- Win32::GetOSVersion
+(W portable) The hexadecimal number you specified is larger than 2**32-1
+(4294967295) and therefore non-portable between systems. See
+L<perlport> for more on portability concerns.
-The remaining functions are unchanged and continue to return C<undef> on
-error even in list context.
+=item Ill-formed CRTL environ value "%s"
-The Win32::SetLastError(ERROR) function has been added as a complement
-to the Win32::GetLastError() function.
+(W internal) A warning peculiar to VMS. Perl tried to read the CRTL's internal
+environ array, and encountered an element without the C<=> delimiter
+used to spearate keys from values. The element is ignored.
-The new Win32::GetFullPathName(FILENAME) returns the full absolute
-pathname for FILENAME in scalar context. In list context it returns
-a two-element list containing the fully qualified directory name and
-the filename. See L<Win32>.
+=item Ill-formed message in prime_env_iter: |%s|
-=item DBM Filters
+(W internal) A warning peculiar to VMS. Perl tried to read a logical name
+or CLI symbol definition when preparing to iterate over %ENV, and
+didn't see the expected delimiter between key and value, so the
+line was ignored.
-A new feature called "DBM Filters" has been added to all the
-DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
-DBM Filters add four new methods to each DBM module:
+=item Illegal binary digit %s
- filter_store_key
- filter_store_value
- filter_fetch_key
- filter_fetch_value
+(F) You used a digit other than 0 or 1 in a binary number.
-These can be used to filter key-value pairs before the pairs are
-written to the database or just after they are read from the database.
-See L<perldbmfilter> for further information.
+=item Illegal binary digit %s ignored
-=back
+(W digit) You may have tried to use a digit other than 0 or 1 in a binary number.
+Interpretation of the binary number stopped before the offending digit.
-=head2 Pragmata
+=item Illegal number of bits in vec
-C<use attrs> is now obsolete, and is only provided for
-backward-compatibility. It's been replaced by the C<sub : attributes>
-syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
+(F) The number of bits in vec() (the third argument) must be a power of
+two from 1 to 32 (or 64, if your platform supports that).
-C<use utf8> to enable UTF-8 and Unicode support.
+=item Integer overflow in %s number
-Lexical warnings pragma, C<use warnings;>, to control optional warnings.
-See L<perllexwarn>.
+(W overflow) The hexadecimal, octal or binary number you have specified either
+as a literal or as an argument to hex() or oct() is too big for your
+architecture, and has been converted to a floating point number. On a
+32-bit architecture the largest hexadecimal, octal or binary number
+representable without overflow is 0xFFFFFFFF, 037777777777, or
+0b11111111111111111111111111111111 respectively. Note that Perl
+transparently promotes all numbers to a floating point representation
+internally--subject to loss of precision errors in subsequent
+operations.
-C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
-...). Currently only one subpragma implemented, "use filetest
-'access';", that uses access(2) or equivalent to check permissions
-instead of using stat(2) as usual. This matters in filesystems
-where there are ACLs (access control lists): the stat(2) might lie,
-but access(2) knows better.
+=item Invalid %s attribute: %s
-=head1 Utility Changes
+The indicated attribute for a subroutine or variable was not recognized
+by Perl or by a user-supplied handler. See L<attributes>.
-=head2 h2ph
+=item Invalid %s attributes: %s
-[TODO - Kurt Starsinic <kstar@chapin.edu>]
+The indicated attributes for a subroutine or variable were not recognized
+by Perl or by a user-supplied handler. See L<attributes>.
-=head2 perlcc
+=item invalid [] range "%s" in regexp
-C<perlcc> now supports the C and Bytecode backends. By default,
-it generates output from the simple C backend rather than the
-optimized C backend.
+The offending range is now explicitly displayed.
-Support for non-Unix platforms has been improved.
+=item Invalid separator character %s in attribute list
-=head2 h2xs
+(F) Something other than a colon or whitespace was seen between the
+elements of an attribute list. If the previous attribute
+had a parenthesised parameter list, perhaps that list was terminated
+too soon. See L<attributes>.
-change#4232
-[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
+=item Invalid separator character %s in subroutine attribute list
-=head1 Documentation Changes
+(F) Something other than a colon or whitespace was seen between the
+elements of a subroutine attribute list. If the previous attribute
+had a parenthesised parameter list, perhaps that list was terminated
+too soon.
-=over 4
+=item leaving effective %s failed
-=item perlapi.pod
+(F) While under the C<use filetest> pragma, switching the real and
+effective uids or gids failed.
-The official list of public Perl API functions.
+=item Lvalue subs returning %s not implemented yet
-=item perlcompile.pod
+(F) Due to limitations in the current implementation, array and hash
+values cannot be returned in subroutines used in lvalue context.
+See L<perlsub/"Lvalue subroutines">.
-An introduction to using the Perl Compiler suite.
+=item Method %s not permitted
-=item perlfilter.pod
+See Server error.
-An introduction to writing Perl source filters.
+=item Missing %sbrace%s on \N{}
-=item perlhack.pod
+(F) Wrong syntax of character name literal C<\N{charname}> within
+double-quotish context.
-Some guidelines for hacking the Perl source code.
+=item Missing command in piped open
-=item perlintern.pod
+(W pipe) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
+construction, but the command was missing or blank.
-A list of internal functions in the Perl source code.
-(List is currently empty.)
+=item Missing name in "my sub"
-=item perlopentut.pod
+(F) The reserved syntax for lexically scoped subroutines requires that they
+have a name with which they can be found.
-A tutorial on using open() effectively.
+=item No %s specified for -%c
-=item perlreftut.pod
+(F) The indicated command line switch needs a mandatory argument, but
+you haven't specified one.
-A tutorial that introduces the essentials of references.
+=item No package name allowed for variable %s in "our"
-=item perlboot.pod
+(F) Fully qualified variable names are not allowed in "our" declarations,
+because that doesn't make much sense under existing semantics. Such
+syntax is reserved for future extensions.
-A tutorial for beginners on object-oriented Perl.
+=item No space allowed after -%c
-=item perltootc.pod
+(F) The argument to the indicated command line switch must follow immediately
+after the switch, without intervening spaces.
-A tutorial on managing class data for object modules.
+=item no UTC offset information; assuming local time is UTC
-=item perlunicode.pod
+(S) A warning peculiar to VMS. Perl was unable to find the local
+timezone offset, so it's assuming that local system time is equivalent
+to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
+to translate to the number of seconds which need to be added to UTC to
+get local time.
-An introduction to Unicode support features in Perl.
+=item Octal number > 037777777777 non-portable
-=back
+(W portable) The octal number you specified is larger than 2**32-1 (4294967295)
+and therefore non-portable between systems. See L<perlport> for more
+on portability concerns.
-=head1 New or Changed Diagnostics
+See also L<perlport> for writing portable code.
-=over 4
+=item panic: del_backref
-=item "%s" variable %s masks earlier declaration in same %s
+(P) Failed an internal consistency check while trying to reset a weak
+reference.
-(W) A "my" or "our" variable has been redeclared in the current scope or statement,
-effectively eliminating all access to the previous instance. This is almost
-always a typographical error. Note that the earlier variable will still exist
-until the end of the scope or until all closure referents to it are
-destroyed.
+=item panic: kid popen errno read
-=item "my sub" not yet implemented
+(F) forked child returned an incomprehensible message about its errno.
-(F) Lexically scoped subroutines are not yet implemented. Don't try that
-yet.
+=item panic: magic_killbackrefs
-=item "our" variable %s redeclared
+(P) Failed an internal consistency check while trying to reset all weak
+references to an object.
-(W) You seem to have already declared the same global once before in the
-current lexical scope.
+=item Parentheses missing around "%s" list
-=item '!' allowed only after types %s
+(W parenthesis) You said something like
-(F) The '!' is allowed in pack() and unpack() only after certain types.
-See L<perlfunc/pack>.
+ my $foo, $bar = @_;
-=item / cannot take a count
+when you meant
-(F) You had an unpack template indicating a counted-length string,
-but you have also specified an explicit size for the string.
-See L<perlfunc/pack>.
+ my ($foo, $bar) = @_;
-=item / must be followed by a, A or Z
+Remember that "my", "our", and "local" bind tighter than comma.
-(F) You had an unpack template indicating a counted-length string,
-which must be followed by one of the letters a, A or Z
-to indicate what sort of string is to be unpacked.
-See L<perlfunc/pack>.
+=item Possible Y2K bug: %s
-=item / must be followed by a*, A* or Z*
+(W y2k) You are concatenating the number 19 with another number, which
+could be a potential Year 2000 problem.
-(F) You had a pack template indicating a counted-length string,
-Currently the only things that can have their length counted are a*, A* or Z*.
-See L<perlfunc/pack>.
+=item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
-=item / must follow a numeric type
+(W deprecated) You have written somehing like this:
-(F) You had an unpack template that contained a '#',
-but this did not follow some numeric unpack specification.
-See L<perlfunc/pack>.
+ sub doit
+ {
+ use attrs qw(locked);
+ }
-=item /%s/: Unrecognized escape \\%c passed through
+You should use the new declaration syntax instead.
-(W) You used a backslash-character combination which is not recognized
-by Perl. This combination appears in an interpolated variable or a
-C<'>-delimited regular expression. The character was understood literally.
+ sub doit : locked
+ {
+ ...
-=item /%s/: Unrecognized escape \\%c in character class passed through
+The C<use attrs> pragma is now obsolete, and is only provided for
+backward-compatibility. See L<perlsub/"Subroutine Attributes">.
-(W) You used a backslash-character combination which is not recognized
-by Perl inside character classes. The character was understood literally.
-=item /%s/ should probably be written as "%s"
+=item Premature end of script headers
-(W) You have used a pattern where Perl expected to find a string,
-as in the first argument to C<join>. Perl will treat the true
-or false result of matching the pattern against $_ as the string,
-which is probably not what you had in mind.
+See Server error.
-=item %s() called too early to check prototype
+=item Repeat count in pack overflows
-(W) You've called a function that has a prototype before the parser saw a
-definition or declaration for it, and Perl could not check that the call
-conforms to the prototype. You need to either add an early prototype
-declaration for the subroutine in question, or move the subroutine
-definition ahead of the call to get proper prototype checking. Alternatively,
-if you are certain that you're calling the function correctly, you may put
-an ampersand before the name to avoid the warning. See L<perlsub>.
+(F) You can't specify a repeat count so large that it overflows
+your signed integers. See L<perlfunc/pack>.
-=item %s argument is not a HASH or ARRAY element
+=item Repeat count in unpack overflows
-(F) The argument to exists() must be a hash or array element, such as:
+(F) You can't specify a repeat count so large that it overflows
+your signed integers. See L<perlfunc/unpack>.
+
+=item realloc() of freed memory ignored
- $foo{$bar}
- $ref->[12]->["susie"]
+(S) An internal routine called realloc() on something that had already
+been freed.
-=item %s argument is not a HASH or ARRAY element or slice
+=item Reference is already weak
-(F) The argument to delete() must be either a hash or array element, such as:
+(W misc) You have attempted to weaken a reference that is already weak.
+Doing so has no effect.
- $foo{$bar}
- $ref->[12]->["susie"]
+=item setpgrp can't take arguments
-or a hash or array slice, such as:
+(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
+unlike POSIX setpgid(), which takes a process ID and process group ID.
- @foo[$bar, $baz, $xyzzy]
- @{$ref->[12]}{"susie", "queue"}
+=item Strange *+?{} on zero-length expression
-=item %s argument is not a subroutine name
+(W regexp) You applied a regular expression quantifier in a place where it
+makes no sense, such as on a zero-width assertion.
+Try putting the quantifier inside the assertion instead. For example,
+the way to match "abc" provided that it is followed by three
+repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
-(F) The argument to exists() for C<exists &sub> must be a subroutine
-name, and not a subroutine call. C<exists &sub()> will generate this error.
+=item switching effective %s is not implemented
-=item %s package attribute may clash with future reserved word: %s
+(F) While under the C<use filetest> pragma, we cannot switch the
+real and effective uids or gids.
-(W) A lowercase attribute name was used that had a package-specific handler.
-That name might have a meaning to Perl itself some day, even though it
-doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
-See L<attributes>.
+=item This Perl can't reset CRTL environ elements (%s)
-=item (in cleanup) %s
+=item This Perl can't set CRTL environ elements (%s=%s)
-(W) This prefix usually indicates that a DESTROY() method raised
-the indicated exception. Since destructors are usually called by
-the system at arbitrary points during execution, and often a vast
-number of times, the warning is issued only once for any number
-of failures that would otherwise result in the same message being
-repeated.
+(W internal) Warnings peculiar to VMS. You tried to change or delete an element
+of the CRTL's internal environ array, but your copy of Perl wasn't
+built with a CRTL that contained the setenv() function. You'll need to
+rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
+L<perlvms>) so that the environ array isn't the target of the change to
+%ENV which produced the warning.
-Failure of user callbacks dispatched using the C<G_KEEPERR> flag
-could also result in this warning. See L<perlcall/G_KEEPERR>.
+=item Too late to run %s block
-=item <> should be quotes
+(W void) A CHECK or INIT block is being defined during run time proper,
+when the opportunity to run them has already passed. Perhaps you are
+loading a file with C<require> or C<do> when you should be using
+C<use> instead. Or perhaps you should put the C<require> or C<do>
+inside a BEGIN block.
-(F) You wrote C<require E<lt>fileE<gt>> when you should have written
-C<require 'file'>.
+=item Unknown open() mode '%s'
-=item Attempt to join self
+(F) The second argument of 3-argument open() is not among the list
+of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
+C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
-(F) You tried to join a thread from within itself, which is an
-impossible task. You may be joining the wrong thread, or you may
-need to move the join() to some other thread.
+=item Unknown process %x sent message to prime_env_iter: %s
-=item Bad evalled substitution pattern
+(P) An error peculiar to VMS. Perl was reading values for %ENV before
+iterating over it, and someone else stuck a message in the stream of
+data Perl expected. Someone's very confused, or perhaps trying to
+subvert Perl's population of %ENV for nefarious purposes.
-(F) You've used the /e switch to evaluate the replacement for a
-substitution, but perl found a syntax error in the code to evaluate,
-most likely an unexpected right brace '}'.
+=item Unrecognized escape \\%c passed through
-=item Bad realloc() ignored
+(W misc) You used a backslash-character combination which is not recognized
+by Perl. The character was understood literally.
-(S) An internal routine called realloc() on something that had never been
-malloc()ed in the first place. Mandatory, but can be disabled by
-setting environment variable C<PERL_BADFREE> to 1.
+=item Unterminated attribute parameter in attribute list
-=item Bareword found in conditional
+(F) The lexer saw an opening (left) parenthesis character while parsing an
+attribute list, but the matching closing (right) parenthesis
+character was not found. You may need to add (or remove) a backslash
+character to get your parentheses to balance. See L<attributes>.
-(W) The compiler found a bareword where it expected a conditional,
-which often indicates that an || or && was parsed as part of the
-last argument of the previous construct, for example:
+=item Unterminated attribute list
- open FOO || die;
+(F) The lexer found something other than a simple identifier at the start
+of an attribute, and it wasn't a semicolon or the start of a
+block. Perhaps you terminated the parameter list of the previous attribute
+too soon. See L<attributes>.
-It may also indicate a misspelled constant that has been interpreted
-as a bareword:
+=item Unterminated attribute parameter in subroutine attribute list
- use constant TYPO => 1;
- if (TYOP) { print "foo" }
+(F) The lexer saw an opening (left) parenthesis character while parsing a
+subroutine attribute list, but the matching closing (right) parenthesis
+character was not found. You may need to add (or remove) a backslash
+character to get your parentheses to balance.
-The C<strict> pragma is useful in avoiding such errors.
+=item Unterminated subroutine attribute list
-=item Binary number > 0b11111111111111111111111111111111 non-portable
+(F) The lexer found something other than a simple identifier at the start
+of a subroutine attribute, and it wasn't a semicolon or the start of a
+block. Perhaps you terminated the parameter list of the previous attribute
+too soon.
-(W) The binary number you specified is larger than 2**32-1
-(4294967295) and therefore non-portable between systems. See
-L<perlport> for more on portability concerns.
+=item Value of CLI symbol "%s" too long
-=item Bit vector size > 32 non-portable
+(W misc) A warning peculiar to VMS. Perl tried to read the value of an %ENV
+element from a CLI symbol table, and found a resultant string longer
+than 1024 characters. The return value has been truncated to 1024
+characters.
-(W) Using bit vector sizes larger than 32 is non-portable.
+=item Version number must be a constant number
-=item Buffer overflow in prime_env_iter: %s
+(P) The attempt to translate a C<use Module n.n LIST> statement into
+its equivalent C<BEGIN> block found an internal inconsistency with
+the version number.
-(W) A warning peculiar to VMS. While Perl was preparing to iterate over
-%ENV, it encountered a logical name or symbol definition which was too long,
-so it was truncated to the string shown.
+=back
-=item Can't check filesystem of script "%s"
+=head1 New tests
-(P) For some reason you can't check the filesystem of the script for nosuid.
+=over 4
-=item Can't declare class for non-scalar %s in "%s"
+=item lib/attrs
-(S) Currently, only scalar variables can declared with a specific class
-qualifier in a "my" or "our" declaration. The semantics may be extended
-for other types of variables in future.
+Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
-=item Can't declare %s in "%s"
+=item lib/env
-(F) Only scalar, array, and hash variables may be declared as "my" or
-"our" variables. They must have ordinary identifiers as names.
+Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
-=item Can't ignore signal CHLD, forcing to default
+=item lib/env-array
-(W) Perl has detected that it is being run with the SIGCHLD signal
-(sometimes known as SIGCLD) disabled. Since disabling this signal
-will interfere with proper determination of exit status of child
-processes, Perl has reset the signal to its default value.
-This situation typically indicates that the parent program under
-which Perl may be running (e.g. cron) is being very careless.
+Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
-=item Can't modify non-lvalue subroutine call
+=item lib/io_const
-(F) Subroutines meant to be used in lvalue context should be declared as
-such, see L<perlsub/"Lvalue subroutines">.
+IO constants (SEEK_*, _IO*).
-=item Can't read CRTL environ
+=item lib/io_dir
-(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
-from the CRTL's internal environment array and discovered the array was
-missing. You need to figure out where your CRTL misplaced its environ
-or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
+Directory-related IO methods (new, read, close, rewind, tied delete).
-=item Can't remove %s: %s, skipping file
+=item lib/io_multihomed
-(S) You requested an inplace edit without creating a backup file. Perl
-was unable to remove the original file to replace it with the modified
-file. The file was left unmodified.
+INET sockets with multi-homed hosts.
-=item Can't return %s from lvalue subroutine
+=item lib/io_poll
-(F) Perl detected an attempt to return illegal lvalues (such
-as temporary or readonly values) from a subroutine used as an lvalue.
-This is not allowed.
+IO poll().
-=item Can't weaken a nonreference
+=item lib/io_unix
-(F) You attempted to weaken something that was not a reference. Only
-references can be weakened.
+UNIX sockets.
-=item Character class [:%s:] unknown
+=item op/attrs
-(F) The class in the character class [: :] syntax is unknown.
-See L<perlre>.
+Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
-=item Character class syntax [%s] belongs inside character classes
+=item op/filetest
-(W) The character class constructs [: :], [= =], and [. .] go
-I<inside> character classes, the [] are part of the construct,
-for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
-are not currently implemented; they are simply placeholders for
-future extensions.
+File test operators.
-=item Constant is not %s reference
+=item op/lex_assign
-(F) A constant value (perhaps declared using the C<use constant> pragma)
-is being dereferenced, but it amounts to the wrong type of reference. The
-message indicates the type of reference that was expected. This usually
-indicates a syntax error in dereferencing the constant value.
-See L<perlsub/"Constant Functions"> and L<constant>.
+Verify operations that access pad objects (lexicals and temporaries).
-=item constant(%s): %%^H is not localized
+=item op/exists_sub
-(F) When setting compile-time-lexicalized hash %^H one should set the
-corresponding bit of $^H as well.
+Verify C<exists &sub> operations.
-=item constant(%s): %s
+=back
-(F) Compile-time-substitutions (such as overloaded constants and
-character names) were not correctly set up.
+=head1 Incompatible Changes
-=item defined(@array) is deprecated
+=head2 Perl Source Incompatibilities
-(D) defined() is not usually useful on arrays because it checks for an
-undefined I<scalar> value. If you want to see if the array is empty,
-just use C<if (@array) { # not empty }> for example.
+Beware that any new warnings that have been added or old ones
+that have been enhanced are B<not> considered incompatible changes.
-=item defined(%hash) is deprecated
+Since all new warnings must be explicitly requested via the C<-w>
+switch or the C<warnings> pragma, it is ultimately the programmer's
+responsibility to ensure that warnings are enabled judiciously.
-(D) defined() is not usually useful on hashes because it checks for an
-undefined I<scalar> value. If you want to see if the hash is empty,
-just use C<if (%hash) { # not empty }> for example.
+=over 4
-=item Did not produce a valid header
+=item CHECK is a new keyword
-See Server error.
+All subroutine definitions named CHECK are now special. See
+C</"Support for CHECK blocks"> for more information.
-=item Did you mean "local" instead of "our"?
+=item Treatment of list slices of undef has changed
-(W) Remember that "our" does not localize the declared global variable.
-You have declared it again in the same lexical scope, which seems superfluous.
+There is a potential incompatibility in the behavior of list slices
+that are comprised entirely of undefined values.
+See L</"Behavior of list slices is more consistent">.
-=item Document contains no data
+=head2 Format of $English::PERL_VERSION is different
-See Server error.
+The English module now sets $PERL_VERSION to $^V (a string value) rather
+than C<$]> (a numeric value). This is a potential incompatibility.
+Send us a report via perlbug if you are affected by this.
-=item entering effective %s failed
+See L</"Improved Perl version numbering system"> for the reasons for
+this change.
-(F) While under the C<use filetest> pragma, switching the real and
-effective uids or gids failed.
+=item Literals of the form C<1.2.3> parse differently
-=item false [] range "%s" in regexp
+Previously, numeric literals with more than one dot in them were
+interpreted as a floating point number concatenated with one or more
+numbers. Such "numbers" are now parsed as strings composed of the
+specified ordinals.
-(W) A character class range must start and end at a literal character, not
-another character class like C<\d> or C<[:alpha:]>. The "-" in your false
-range is interpreted as a literal "-". Consider quoting the "-", "\-".
-See L<perlre>.
+For example, C<print 97.98.99> used to output C<97.9899> in earlier
+versions, but now prints C<abc>.
-=item Filehandle %s opened only for output
+See L</"Support for strings represented as a vector of ordinals">.
-(W) You tried to read from a filehandle opened only for writing. If you
-intended it to be a read/write filehandle, you needed to open it with
-"+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
-you intended only to read from the file, use "E<lt>". See
-L<perlfunc/open>.
+=item Possibly changed pseudo-random number generator
-=item flock() on closed filehandle %s
+Perl programs that depend on reproducing a specific set of pseudo-random
+numbers may now produce different output due to improvements made to the
+rand() builtin. You can use C<sh Configure -Drandfunc=rand> to obtain
+the old behavior.
-(W) The filehandle you're attempting to flock() got itself closed some
-time before now. Check your logic flow. flock() operates on filehandles.
-Are you attempting to call flock() on a dirhandle by the same name?
+See L</"Better pseudo-random number generator">.
-=item Global symbol "%s" requires explicit package name
+=item Hashing function for hash keys has changed
-(F) You've said "use strict vars", which indicates that all variables
-must either be lexically scoped (using "my"), declared beforehand using
-"our", or explicitly qualified to say which package the global variable
-is in (using "::").
+Even though Perl hashes are not order preserving, the apparently
+random order encountered when iterating on the contents of a hash
+is actually determined by the hashing algorithm used. Improvements
+in the algorithm may yield a random order that is B<different> from
+that of previous versions, especially when iterating on hashes.
-=item Hexadecimal number > 0xffffffff non-portable
+See L</"Better worst-case behavior of hashes"> for additional
+information.
-(W) The hexadecimal number you specified is larger than 2**32-1
-(4294967295) and therefore non-portable between systems. See
-L<perlport> for more on portability concerns.
+=item C<undef> fails on read only values
-=item Ill-formed CRTL environ value "%s"
+Using the C<undef> operator on a readonly value (such as $1) has
+the same effect as assigning C<undef> to the readonly value--it
+throws an exception.
-(W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
-environ array, and encountered an element without the C<=> delimiter
-used to spearate keys from values. The element is ignored.
+=item Close-on-exec bit may be set on pipe and socket handles
-=item Ill-formed message in prime_env_iter: |%s|
+Pipe and socket handles are also now subject to the close-on-exec
+behavior determined by the special variable $^F.
-(W) A warning peculiar to VMS. Perl tried to read a logical name
-or CLI symbol definition when preparing to iterate over %ENV, and
-didn't see the expected delimiter between key and value, so the
-line was ignored.
+See L</"More consistent close-on-exec behavior">.
-=item Illegal binary digit %s
+=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
-(F) You used a digit other than 0 or 1 in a binary number.
+Perl 5.004 deprecated the interpretation of C<$$1> and
+similar within interpolated strings to mean C<$$ . "1">,
+but still allowed it.
-=item Illegal binary digit %s ignored
+In Perl 5.6.0 and later, C<"$$1"> always means C<"${$1}">.
-(W) You may have tried to use a digit other than 0 or 1 in a binary number.
-Interpretation of the binary number stopped before the offending digit.
+=item delete(), values() and C<\(%h)> operate on aliases to values, not copies
-=item Illegal number of bits in vec
+delete(), each(), values() and hashes in a list context return the actual
+values in the hash, instead of copies (as they used to in earlier
+versions). Typical idioms for using these constructs copy the
+returned values, but this can make a significant difference when
+creating references to the returned values. Keys in the hash are still
+returned as copies when iterating on a hash.
-(F) The number of bits in vec() (the third argument) must be a power of
-two from 1 to 32 (or 64, if your platform supports that).
+See also L</"delete(), each(), values() and hash iteration are faster">.
-=item Integer overflow in %s number
+=item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
-(W) The hexadecimal, octal or binary number you have specified either
-as a literal or as an argument to hex() or oct() is too big for your
-architecture, and has been converted to a floating point number. On a
-32-bit architecture the largest hexadecimal, octal or binary number
-representable without overflow is 0xFFFFFFFF, 037777777777, or
-0b11111111111111111111111111111111 respectively. Note that Perl
-transparently promotes all numbers to a floating point representation
-internally--subject to loss of precision errors in subsequent
-operations.
+vec() generates a run-time error if the BITS argument is not
+a valid power-of-two integer.
-=item Invalid %s attribute: %s
+=item Text of some diagnostic output has changed
-The indicated attribute for a subroutine or variable was not recognized
-by Perl or by a user-supplied handler. See L<attributes>.
+Most references to internal Perl operations in diagnostics
+have been changed to be more descriptive. This may be an
+issue for programs that may incorrectly rely on the exact
+text of diagnostics for proper functioning.
-=item Invalid %s attributes: %s
+=item C<%@> has been removed
-The indicated attributes for a subroutine or variable were not recognized
-by Perl or by a user-supplied handler. See L<attributes>.
+The undocumented special variable C<%@> that used to accumulate
+"background" errors (such as those that happen in DESTROY())
+has been removed, because it could potentially result in memory
+leaks.
-=item invalid [] range "%s" in regexp
+=item Parenthesized not() behaves like a list operator
-The offending range is now explicitly displayed.
+The C<not> operator now falls under the "if it looks like a function,
+it behaves like a function" rule.
-=item Invalid separator character %s in attribute list
+As a result, the parenthesized form can be used with C<grep> and C<map>.
+The following construct used to be a syntax error before, but it works
+as expected now:
-(F) Something other than a colon or whitespace was seen between the
-elements of an attribute list. If the previous attribute
-had a parenthesised parameter list, perhaps that list was terminated
-too soon. See L<attributes>.
+ grep not($_), @things;
-=item Invalid separator character %s in subroutine attribute list
+On the other hand, using C<not> with a literal list slice may not
+work. The following previously allowed construct:
-(F) Something other than a colon or whitespace was seen between the
-elements of a subroutine attribute list. If the previous attribute
-had a parenthesised parameter list, perhaps that list was terminated
-too soon.
+ print not (1,2,3)[0];
-=item leaving effective %s failed
+needs to be written with additional parentheses now:
-(F) While under the C<use filetest> pragma, switching the real and
-effective uids or gids failed.
+ print not((1,2,3)[0]);
-=item Lvalue subs returning %s not implemented yet
+The behavior remains unaffected when C<not> is not followed by parentheses.
-(F) Due to limitations in the current implementation, array and hash
-values cannot be returned in subroutines used in lvalue context.
-See L<perlsub/"Lvalue subroutines">.
+=item Semantics of bareword prototype C<(*)> have changed
-=item Method %s not permitted
+The semantics of the bareword prototype C<*> have changed. Perl 5.005
+always coerced simple scalar arguments to a typeglob, which wasn't useful
+in situations where the subroutine must distinguish between a simple
+scalar and a typeglob. The new behavior is to not coerce bareword
+arguments to a typeglob. The value will always be visible as either
+a simple scalar or as a reference to a typeglob.
-See Server error.
+See L</"More functional bareword prototype (*)">.
-=item Missing %sbrace%s on \N{}
+=head2 Semantics of bit operators may have changed on 64-bit platforms
-(F) Wrong syntax of character name literal C<\N{charname}> within
-double-quotish context.
+If your platform is either natively 64-bit or if Perl has been
+configured to used 64-bit integers, i.e., $Config{ivsize} is 8,
+there may be a potential incompatibility in the behavior of bitwise
+numeric operators (& | ^ ~ << >>). These operators used to strictly
+operate on the lower 32 bits of integers in previous versions, but now
+operate over the entire native integral width. In particular, note
+that unary C<~> will produce different results on platforms that have
+different $Config{ivsize}. For portability, be sure to mask off
+the excess bits in the result of unary C<~>, e.g., C<~$x & 0xffffffff>.
-=item Missing command in piped open
+See L</"Bit operators support full native integer width">.
-(W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
-construction, but the command was missing or blank.
+=head2 More builtins taint their results
-=item Missing name in "my sub"
+As described in L</"Improved security features">, there may be more
+sources of taint in a Perl program.
-(F) The reserved syntax for lexically scoped subroutines requires that they
-have a name with which they can be found.
+To avoid these new tainting behaviors, you can build Perl with the
+Configure option C<-Accflags=-DINCOMPLETE_TAINTS>. Beware that the
+ensuing perl binary may be insecure.
-=item No %s specified for -%c
+=back
-(F) The indicated command line switch needs a mandatory argument, but
-you haven't specified one.
+=head2 C Source Incompatibilities
-=item No package name allowed for variable %s in "our"
+=over 4
-(F) Fully qualified variable names are not allowed in "our" declarations,
-because that doesn't make much sense under existing semantics. Such
-syntax is reserved for future extensions.
+=item C<PERL_POLLUTE>
-=item No space allowed after -%c
+Release 5.005 grandfathered old global symbol names by providing preprocessor
+macros for extension source compatibility. As of release 5.6.0, these
+preprocessor definitions are not available by default. You need to explicitly
+compile perl with C<-DPERL_POLLUTE> to get these definitions. For
+extensions still using the old symbols, this option can be
+specified via MakeMaker:
-(F) The argument to the indicated command line switch must follow immediately
-after the switch, without intervening spaces.
+ perl Makefile.PL POLLUTE=1
-=item no UTC offset information; assuming local time is UTC
+=item C<PERL_IMPLICIT_CONTEXT>
-(S) A warning peculiar to VMS. Perl was unable to find the local
-timezone offset, so it's assuming that local system time is equivalent
-to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
-to translate to the number of seconds which need to be added to UTC to
-get local time.
+This new build option provides a set of macros for all API functions
+such that an implicit interpreter/thread context argument is passed to
+every API function. As a result of this, something like C<sv_setsv(foo,bar)>
+amounts to a macro invocation that actually translates to something like
+C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
+to not have any significant source compatibility issues, the difference
+between a macro and a real function call will need to be considered.
-=item Octal number > 037777777777 non-portable
+This means that there B<is> a source compatibility issue as a result of
+this if your extensions attempt to use pointers to any of the Perl API
+functions.
-(W) The octal number you specified is larger than 2**32-1 (4294967295)
-and therefore non-portable between systems. See L<perlport> for more
-on portability concerns.
+Note that the above issue is not relevant to the default build of
+Perl, whose interfaces continue to match those of prior versions
+(but subject to the other options described here).
-See also L<perlport> for writing portable code.
+See L<perlguts/"The Perl API"> for detailed information on the
+ramifications of building Perl with this option.
-=item panic: del_backref
+ NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
+ with one of -Dusethreads, -Dusemultiplicity, or both. It is not
+ intended to be enabled by users at this time.
-(P) Failed an internal consistency check while trying to reset a weak
-reference.
+=item C<PERL_POLLUTE_MALLOC>
-=item panic: kid popen errno read
+Enabling Perl's malloc in release 5.005 and earlier caused the namespace of
+the system's malloc family of functions to be usurped by the Perl versions,
+since by default they used the same names. Besides causing problems on
+platforms that do not allow these functions to be cleanly replaced, this
+also meant that the system versions could not be called in programs that
+used Perl's malloc. Previous versions of Perl have allowed this behaviour
+to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
+definitions.
-(F) forked child returned an incomprehensible message about its errno.
+As of release 5.6.0, Perl's malloc family of functions have default names
+distinct from the system versions. You need to explicitly compile perl with
+C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
+and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
+the default.
-=item panic: magic_killbackrefs
+Note that these functions do B<not> constitute Perl's memory allocation API.
+See L<perlguts/"Memory Allocation"> for further information about that.
-(P) Failed an internal consistency check while trying to reset all weak
-references to an object.
+=back
-=item Parentheses missing around "%s" list
+=head2 Compatible C Source API Changes
-(W) You said something like
+=over
- my $foo, $bar = @_;
+=item C<PATCHLEVEL> is now C<PERL_VERSION>
-when you meant
+The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
+are now available by default from perl.h, and reflect the base revision,
+patchlevel, and subversion respectively. C<PERL_REVISION> had no
+prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
+previously available as C<PATCHLEVEL> and C<SUBVERSION>.
- my ($foo, $bar) = @_;
+The new names cause less pollution of the B<cpp> namespace and reflect what
+the numbers have come to stand for in common practice. For compatibility,
+the old names are still supported when F<patchlevel.h> is explicitly
+included (as required before), so there is no source incompatibility
+from the change.
-Remember that "my", "our", and "local" bind tighter than comma.
+=back
-=item Possible Y2K bug: %s
+=head2 Binary Incompatibilities
-(W) You are concatenating the number 19 with another number, which
-could be a potential Year 2000 problem.
+In general, the default build of this release is expected to be binary
+compatible for extensions built with the 5.005 release or its maintenance
+versions. However, specific platforms may have broken binary compatibility
+due to changes in the defaults used in hints files. Therefore, please be
+sure to always check the platform-specific README files for any notes to
+the contrary.
-=item Premature end of script headers
+The usethreads or usemultiplicity builds are B<not> binary compatible
+with the corresponding builds in 5.005.
-See Server error.
+On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
+among others), purely internal symbols such as parser functions and the
+run time opcodes are not exported by default. Perl 5.005 used to export
+all functions irrespective of whether they were considered part of the
+public API or not.
-=item Repeat count in pack overflows
+For the full list of public API functions, see L<perlapi>.
-(F) You can't specify a repeat count so large that it overflows
-your signed integers. See L<perlfunc/pack>.
+=head1 Known Problems
-=item Repeat count in unpack overflows
+=head2 Thread test failures
-(F) You can't specify a repeat count so large that it overflows
-your signed integers. See L<perlfunc/unpack>.
+The subtests 19 and 20 of lib/thr5005.t test are known to fail due to
+fundamental problems in the 5.005 threading implementation. These are
+not new failures--Perl 5.005_0x has the same bugs, but didn't have these
+tests.
-=item realloc() of freed memory ignored
+=head2 EBCDIC platforms not supported
-(S) An internal routine called realloc() on something that had already
-been freed.
+In earlier releases of Perl, EBCDIC environments like OS390 (also
+known as Open Edition MVS) and VM-ESA were supported. Due to changes
+required by the UTF-8 (Unicode) support, the EBCDIC platforms are not
+supported in Perl 5.6.0.
-=item Reference is already weak
+=head2 In 64-bit HP-UX the lib/io_multihomed test may hang
-(W) You have attempted to weaken a reference that is already weak.
-Doing so has no effect.
+The lib/io_multihomed test may hang in HP-UX if Perl has been
+configured to be 64-bit. Because other 64-bit platforms do not
+hang in this test, HP-UX is suspect. All other tests pass
+in 64-bit HP-UX. The test attempts to create and connect to
+"multihomed" sockets (sockets which have multiple IP addresses).
-=item setpgrp can't take arguments
+=head2 NEXTSTEP 3.3 POSIX test failure
-(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
-unlike POSIX setpgid(), which takes a process ID and process group ID.
+In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the
+operating system libraries is buggy: the %j format numbers the days of
+a month starting from zero, which, while being logical to programmers,
+will cause the subtests 19 to 27 of the lib/posix test may fail.
-=item Strange *+?{} on zero-length expression
+=head2 Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc
-(W) You applied a regular expression quantifier in a place where it
-makes no sense, such as on a zero-width assertion.
-Try putting the quantifier inside the assertion instead. For example,
-the way to match "abc" provided that it is followed by three
-repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
+If compiled with gcc 2.95 the lib/sdbm test will fail (dump core).
+The cure is to use the vendor cc, it comes with the operating system
+and produces good code.
-=item switching effective %s is not implemented
+=head2 UNICOS/mk CC failures during Configure run
-(F) While under the C<use filetest> pragma, we cannot switch the
-real and effective uids or gids.
+In UNICOS/mk the following errors may appear during the Configure run:
-=item This Perl can't reset CRTL environ elements (%s)
+ Guessing which symbols your C compiler and preprocessor define...
+ CC-20 cc: ERROR File = try.c, Line = 3
+ ...
+ bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
+ ...
+ 4 errors detected in the compilation of "try.c".
-=item This Perl can't set CRTL environ elements (%s=%s)
+The culprit is the broken awk of UNICOS/mk. The effect is fortunately
+rather mild: Perl itself is not adversely affected by the error, only
+the h2ph utility coming with Perl, and that is rather rarely needed
+these days.
-(W) Warnings peculiar to VMS. You tried to change or delete an element
-of the CRTL's internal environ array, but your copy of Perl wasn't
-built with a CRTL that contained the setenv() function. You'll need to
-rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
-L<perlvms>) so that the environ array isn't the target of the change to
-%ENV which produced the warning.
+=head2 Arrow operator and arrays
-=item Unknown open() mode '%s'
+When the left argument to the arrow operator C<< -> >> is an array, or
+the C<scalar> operator operating on an array, the result of the
+operation must be considered erroneous. For example:
-(F) The second argument of 3-argument open() is not among the list
-of valid modes: C<E<lt>>, C<E<gt>>, C<E<gt>E<gt>>, C<+E<lt>>,
-C<+E<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|E<45>>.
+ @x->[2]
+ scalar(@x)->[2]
-=item Unknown process %x sent message to prime_env_iter: %s
+These expressions will get run-time errors in some future release of
+Perl.
-(P) An error peculiar to VMS. Perl was reading values for %ENV before
-iterating over it, and someone else stuck a message in the stream of
-data Perl expected. Someone's very confused, or perhaps trying to
-subvert Perl's population of %ENV for nefarious purposes.
+=head2 Windows 2000
-=item Unrecognized escape \\%c passed through
+Windows 2000 is known to fail test 22 in lib/open3.t (cause unknown at
+this time). That test passes under Windows NT.
-(W) You used a backslash-character combination which is not recognized
-by Perl. The character was understood literally.
+=head2 Experimental features
-=item Unterminated attribute parameter in attribute list
+As discussed above, many features are still experimental. Interfaces and
+implementation of these features are subject to change, and in extreme cases,
+even subject to removal in some future release of Perl. These features
+include the following:
-(F) The lexer saw an opening (left) parenthesis character while parsing an
-attribute list, but the matching closing (right) parenthesis
-character was not found. You may need to add (or remove) a backslash
-character to get your parentheses to balance. See L<attributes>.
+=over 4
-=item Unterminated attribute list
+=item Threads
-(F) The lexer found something other than a simple identifier at the start
-of an attribute, and it wasn't a semicolon or the start of a
-block. Perhaps you terminated the parameter list of the previous attribute
-too soon. See L<attributes>.
+=item Unicode
-=item Unterminated attribute parameter in subroutine attribute list
+=item 64-bit support
-(F) The lexer saw an opening (left) parenthesis character while parsing a
-subroutine attribute list, but the matching closing (right) parenthesis
-character was not found. You may need to add (or remove) a backslash
-character to get your parentheses to balance.
+=item Lvalue subroutines
-=item Unterminated subroutine attribute list
+=item Weak references
-(F) The lexer found something other than a simple identifier at the start
-of a subroutine attribute, and it wasn't a semicolon or the start of a
-block. Perhaps you terminated the parameter list of the previous attribute
-too soon.
+=item The pseudo-hash data type
-=item Value of CLI symbol "%s" too long
+=item The Compiler suite
-(W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
-element from a CLI symbol table, and found a resultant string longer
-than 1024 characters. The return value has been truncated to 1024
-characters.
+=item Internal implementation of file globbing
-=item Version number must be a constant number
+=item The DB module
-(P) The attempt to translate a C<use Module n.n LIST> statement into
-its equivalent C<BEGIN> block found an internal inconsistency with
-the version number.
+=item The regular expression constructs C<(?{ code })> and C<(??{ code })>
=back
=back
-=head1 BUGS
+=head1 Reporting Bugs
If you find what you think is a bug, you might check the
articles recently posted to the comp.lang.perl.misc newsgroup.
Home Page.
If you believe you have an unreported bug, please run the B<perlbug>
-program included with your release. Make sure to trim your bug down
+program included with your release. Be sure to trim your bug down
to a tiny but sufficient test case. Your bug report, along with the
output of C<perl -V>, will be sent off to perlbug@perl.com to be
analysed by the Perl porting team.
projects / p5sagit/p5-mst-13.2.git / blobdiff