=head1 Core Enhancements
+=head2 Interpreter cloning, threads, and concurrency
+
+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.
+
+On the Windows platform, this feature is used to emulate fork() at the
+interpreter level. See L<perlfork> for details about that.
+
+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.
+
+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.
+
+-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.
+
+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.
+
+ NOTE: This is an experimental feature. Implementation details are
+ subject to change.
+
+=head2 Lexically scoped warning categories
+
+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.
+
+=head2 Unicode and UTF-8 support
+
+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.
+
+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.
+
+ 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 Improved Perl version numbering system
+
+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 v5.6.0 will be numbered v5.7.x,
+beginning with v5.7.0, and the next major production release following
+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.
+Send us a report via perlbug if you are affected by this.)
+
+The v1.2.3 syntax is also now legal in Perl.
+See L<Support for strings represented as a vector of ordinals> for more on that.
+
+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 v5.6.0 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 should be read as being
+equivalent to a floating point value of 5.006_001 in the older format,
+stored in C<$]>).
+
+=head2 New syntax for declaring subroutine attributes
+
+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:
+
+ sub mymethod : locked method ;
+ ...
+ sub mymethod : locked method {
+ ...
+ }
+
+ sub othermethod :locked :method ;
+ ...
+ sub othermethod :locked :method {
+ ...
+ }
+
+
+(Note how only the first C<:> is mandatory, and whitespace surrounding
+the C<:> is optional.)
+
+F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
+with the stubs they provide. See L<attributes>.
+
+=head2 File and directory handles can be autovivified
+
+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:
+
+ sub myopen {
+ open my $fh, "@_"
+ or die "Can't open '@_': $!";
+ return $fh;
+ }
+
+ {
+ my $f = myopen("</etc/motd");
+ print <$f>;
+ # $f implicitly closed here
+ }
+
+=head2 open() with more than two arguments
+
+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>.
+
+=head2 64-bit support
+
+Any platform that has 64-bit integers either
+
+ (1) natively as longs or ints
+ (2) via special compiler flags
+ (3) using long long or int64_t
+
+is able to use "quads" (64-bit integers) as follows:
+
+=over 4
+
+=item *
+
+constants (decimal, hexadecimal, octal, binary) in the code
+
+=item *
+
+arguments to oct() and hex()
+
+=item *
+
+arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
+
+=item *
+
+printed as such
+
+=item *
+
+pack() and unpack() "q" and "Q" formats
+
+=item *
+
+in basic arithmetics: + - * / % (NOTE: operating close to the limits
+of the integer values may produce surprising results)
+
+=item *
+
+in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
+to be 32 bits wide but now operate on the full native width.)
+
+=item *
+
+vec()
+
+=back
+
+Note that unless you have the case (a) you will have to configure
+and compile Perl using the -Duse64bitint Configure flag.
+
+ NOTE: The Configure flags -Duselonglong and -Duse64bits have been
+ deprecated. Use -Duse64bitint instead.
+
+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.
+
+Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
+nor -Duse64bitall.
+
+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).
+
+ 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.
+
+=head2 Large file support
+
+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.
+
+ NOTE: The default action is to enable large file support, if
+ available on the platform.
+
+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().
+
+Beware that unless your filesystem also supports "sparse files" seeking
+to umpteen petabytes may be inadvisable.
+
+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.
+
+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.
+
+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.
+
+=head2 Long doubles
+
+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).
+
+=head2 "more bits"
+
+You can "Configure -Dusemorebits" to turn on both the 64-bit support
+and the long double support.
+
+=head2 Enhanced support for sort() subroutines
+
+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>.
+
+For unprototyped sort subroutines, the historical behavior of passing
+the elements to be compared as the global variables $a and $b remains
+unchanged.
+
+=head2 C<sort $coderef @foo> allowed
+
+sort() did not accept a subroutine reference as the comparison
+function in earlier versions. This is now permitted.
+
+=head2 File globbing implemented internally
+
+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.
+
+ NOTE: This is currently an experimental feature. Interfaces and
+ implementation are subject to change.
+
+=item Support for CHECK blocks
+
+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 POSIX character class syntax [: :] supported
+
+For example to match alphabetic characters use /[[:alpha:]]/.
+See L<perlre> for details.
+
+=item Better 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.
+
+These changes should result in better random numbers from rand().
+
+=head2 Improved C<qw//> operator
+
+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().
+
+Thus:
+
+ $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
+
+now correctly prints "3|a", instead of "2|a".
+
+=item Better worst-case behavior of hashes
+
+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.
+
+=head2 pack() format 'Z' supported
+
+The new format type 'Z' is useful for packing and unpacking null-terminated
+strings. See L<perlfunc/"pack">.
+
+=head2 pack() format modifier '!' supported
+
+The new format type modifier '!' is useful for packing and unpacking
+native shorts, ints, and longs. See L<perlfunc/"pack">.
+
+=head2 pack() and unpack() support counted strings
+
+The template character '/' can be used to specify a counted string
+type to be packed or unpacked. See L<perlfunc/"pack">.
+
+=head2 Comments in pack() templates
+
+The '#' character in a template introduces a comment up to
+end of the line. This facilitates documentation of pack()
+templates.
+
+=head2 Weak references
+
+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.
+
+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.
+
+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.
+
+To use this feature, you need the WeakRef package from CPAN, which
+contains additional documentation.
+
+ NOTE: This is an experimental feature. Details are subject to change.
+
+=head2 Binary numbers supported
+
+Binary numbers are now supported as literals, in s?printf formats, and
+C<oct()>:
+
+ $answer = 0b101010;
+ printf "The answer is: %b\n", oct("0b101010");
+
+=head2 Lvalue subroutines
+
+Subroutines can now return modifiable lvalues.
+See L<perlsub/"Lvalue subroutines">.
+
+ NOTE: This is an experimental feature. Details are subject to change.
+
+=head2 Some arrows may be omitted in calls through references
+
+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<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
+required for C<< foo(10)->('bar') >>.
+
+=head2 Boolean assignment operators are legal lvalues
+
+Constructs such as C<($a ||= 2) += 1> are now allowed.
+
+=head2 exists() is supported on subroutine names
+
+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.
+
+=head2 exists() and delete() are supported on array elements
+
+The exists() and delete() builtins now work on simple arrays as well.
+The behavior is similar to that on hash elements.
+
+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.
+
+See L<perlfunc/exists> and L<perlfunc/delete> for examples.
+
+=head2 Pseudo-hashes work better
+
+Dereferencing some types of reference values in a pseudo-hash,
+such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
+been corrected.
+
+When applied to a pseudo-hash element, exists() now reports whether
+the specified value exists, not merely if the key is valid.
+
+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
-=head1 Utility Changes
+=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>.
+
+=item constant
+
+References can now be used.
+
+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.
+
+See L<constant>.
+
+=item charnames
+
+This pragma implements the C<\N> string escape. See L<charnames>.
+
+=item Data::Dumper
+
+A C<Maxdepth> setting can be specified to avoid venturing
+too deeply into deep data structures. See L<Data::Dumper>.
+
+The XSUB implementation of Dump() is now automatically called if the
+C<Useqq> setting is not in use.
+
+Dumping C<qr//> objects works correctly.
+
+=item DB
+
+C<DB> is an experimental module that exposes a clean abstraction
+to Perl's debugging API.
+
+=item DB_File
+
+DB_File can now be built with Berkeley DB versions 1, 2 or 3.
+See C<ext/DB_File/Changes>.
+
+=item Devel::DProf
+
+Devel::DProf, a Perl source code profiler has been added. See
+L<Devel::DProf> and L<dprofpp>.
+
+=item Devel::Peek
+
+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 Dumpvalue
+
+The Dumpvalue module provides screen dumps of Perl data.
+
+=item DynaLoader
+
+DynaLoader now supports a dl_unload_file() function on platforms that
+support unloading shared objects using dlclose().
+
+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.)
+
+=item English
+
+$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
+(a numeric value).
+
+=item Env
+
+Env now supports accessing environment variables like PATH as array
+variables.
+
+=item Fcntl
+
+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.
+
+=item File::Compare
+
+A compare_text() function has been added, which allows custom
+comparison functions. See L<File::Compare>.
+
+=item File::Find
+
+File::Find now works correctly when the wanted() function is either
+autoloaded or is a symbolic reference.
+
+A bug that caused File::Find to lose track of the working directory
+when pruning top-level directories has been fixed.
+
+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.
+
+See L<File::Find>.
+
+=item File::Glob
+
+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 File::Spec
+
+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 File::Spec::Functions
+
+The new File::Spec::Functions modules provides a function interface
+to the File::Spec module. Allows shorthand
+
+ $fullname = catfile($dir1, $dir2, $file);
+
+instead of
+
+ $fullname = File::Spec->catfile($dir1, $dir2, $file);
+
+=item Getopt::Long
+
+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.
+
+Getopt::Long encourages the use of Pod::Usage to produce help
+messages. For example:
+
+ 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;
+
+ __END__
+
+ =head1 NAME
+
+ sample - Using GetOpt::Long and Pod::Usage
+
+ =head1 SYNOPSIS
+
+ sample [options] [file ...]
+
+ Options:
+ -help brief help message
+ -man full documentation
+
+ =head1 OPTIONS
+
+ =over 8
+
+ =item B<-help>
+
+ Print a brief help message and exits.
+
+ =item B<-man>
+
+ Prints the manual page and exits.
+
+ =back
+
+ =head1 DESCRIPTION
+
+ B<This program> will read the given input file(s) and do someting
+ useful with the contents thereof.
+
+ =cut
+
+See L<Pod::Usage> for details.
+
+A bug that prevented the non-option call-back <> from being
+specified as the first argument has been fixed.
+
+To specify the characters < and > as option starters, use ><. Note,
+however, that changing option starters is strongly deprecated.
+
+=item IO
+
+write() and syswrite() will now accept a single-argument
+form of the call, for consistency with Perl's syswrite().
+
+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.
+
+A bug that prevented the IO::Socket::protocol() accessor
+from ever returning the correct value has been corrected.
+
+IO::Socket::connect now uses non-blocking IO instead of alarm()
+to do connect timeouts.
+
+IO::Socket::accept now uses select() instead of alarm() for doing
+timeouts.
+
+IO::Socket::INET->new now sets $! correctly on failure. $@ is
+still set for backwards compatability.
+
+=item JPL
+
+Java Perl Lingo is now distributed with Perl. See jpl/README
+for more information.
+
+=item lib
+
+C<use lib> now weeds out any trailing duplicate entries.
+C<no lib> removes all named entries.
+
+=item Math::BigInt
+
+The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
+and C<~> are now supported on bigints.
+
+=item Math::Complex
+
+The accessor methods Re, Im, arg, abs, rho, and theta can now also
+act as mutators (accessor $z->Re(), mutator $z->Re(3)).
+
+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.
+
+=item Math::Trig
+
+A little bit of radial trigonometry (cylindrical and spherical),
+radial coordinate conversions, and the great circle distance were added.
+
+=item Pod::Parser, Pod::InputObjects
+
+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.
+
+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.
+
+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.
+
+For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
+
+=item Pod::Checker, podchecker
+
+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>.
+
+=item Pod::ParseUtils, Pod::Find
+
+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).
+
+=item Pod::Select, podselect
+
+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>.
+
+=item Pod::Usage, pod2usage
+
+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.
+
+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).
+
+For details and examples, please see L<Pod::Usage>.
+
+=item Pod::Text and Pod::Man
+
+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.
+
+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.
+
+=item SDBM_File
+
+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.
+
+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 Sys::Syslog
+
+Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
+no longer requires syslog.ph to exist.
+
+=item Sys::Hostname
+
+Sys::Hostname now uses XSUBs to call the C library's gethostname() or
+uname() if they exist.
+
+=item Term::ANSIColor
+
+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
+
+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 Win32
+
+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:
+
+ Win32::FsType
+ Win32::GetOSVersion
+
+The remaining functions are unchanged and continue to return C<undef> on
+error even in list context.
+
+The Win32::SetLastError(ERROR) function has been added as a complement
+to the Win32::GetLastError() function.
+
+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 XSLoader
+
+The XSLoader extension is a simpler alternative to DynaLoader.
+See L<XSLoader>.
+
+=item DBM Filters
+
+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:
+
+ filter_store_key
+ filter_store_value
+ filter_fetch_key
+ filter_fetch_value
+
+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.
+
+=back
+
+=head2 Pragmata
+
+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>.
+
+Lexical warnings pragma, C<use warnings;>, to control optional warnings.
+See L<perllexwarn>.
+
+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.
+
+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">.
+
+=head1 Utility Changes
+
+=head2 dprofpp
+
+C<dprofpp> is used to display profile data generated using C<Devel::DProf>.
+See L<dprofpp>.
+
+=head2 find2perl
+
+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.
+
+=head2 h2xs
+
+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.
+
+=head2 perlcc
+
+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.
+
+Support for non-Unix platforms has been improved.
+
+=head2 perldoc
+
+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.
+
+=head2 The Perl Debugger
+
+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.
+
+=head1 Improved Documentation
+
+Many of the platform-specific README files are now part of the perl
+installation. See L<perl> for the complete list.
+
+=over 4
+
+=item perlapi.pod
+
+The official list of public Perl API functions.
+
+=item perlboot.pod
+
+A tutorial for beginners on object-oriented Perl.
+
+=item perlcompile.pod
+
+An introduction to using the Perl Compiler suite.
+
+=item perldbmfilter.pod
+
+A howto document on using the DBM filter facility.
+
+=item perldebug.pod
+
+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.
+
+=item perldebguts.pod
+
+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.
+
+=item perlfork.pod
+
+Notes on the fork() emulation currently available for the Windows platform.
+
+=item perlfilter.pod
+
+An introduction to writing Perl source filters.
+
+=item perlhack.pod
+
+Some guidelines for hacking the Perl source code.
+
+=item perlintern.pod
+
+A list of internal functions in the Perl source code.
+(List is currently empty.)
+
+=item perllexwarn.pod
+
+Introduction and reference information about lexically scoped
+warning categories.
+
+=item perlnumber.pod
+
+Detailed information about numbers as they are represented in Perl.
+
+=item perlopentut.pod
+
+A tutorial on using open() effectively.
+
+=item perlreftut.pod
+
+A tutorial that introduces the essentials of references.
+
+=item perltootc.pod
+
+A tutorial on managing class data for object modules.
+
+=item perltodo.pod
+
+Discussion of the most often wanted features that may someday be
+supported in Perl.
+
+=item perlunicode.pod
+
+An introduction to Unicode support features in Perl.
+
+=back
+
+=head1 Performance enhancements
+
+=head2 Simple sort() using { $a <=> $b } and the like are optimized
+
+Many common sort() operations using a simple inlined block are now
+optimized for faster performance.
+
+=head2 Optimized assignments to lexical variables
+
+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 Faster subroutine calls
+
+Minor changes in how subroutine calls are handled internally
+provide marginal improvements in performance.
+
+=item delete(), each(), values() and hash iteration are faster
+
+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.
+
+=head1 Installation and Configuration Improvements
+
+=head2 -Dusethreads means something different
+
+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".
+
+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.
+
+ NOTE: Support for threads continues to be an experimental feature.
+ Interfaces and implementation are subject to sudden and drastic changes.
+
+=head2 New Configure flags
+
+The following new flags may be enabled on the Configure command line
+by running Configure with C<-Dflag>.
+
+ usemultiplicity
+ usethreads useithreads (new interpreter threads: no Perl API yet)
+ usethreads use5005threads (threads as they were in 5.005)
+
+ use64bitint (equal to now deprecated 'use64bits')
+ use64bitall
+
+ uselongdouble
+ usemorebits
+ uselargefiles
+ usesocks (only SOCKS v5 supported)
+
+=head2 Threadedness and 64-bitness now more daring
+
+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 Long Doubles
+
+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 -Dusemorebits
+
+You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
+See also L<"64-bit support">.
+
+=head2 -Duselargefiles
+
+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.
+
+See L<"Large file support"> for more information.
+
+=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 SOCKS support
+
+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:
+
+ http://www.socks.nec.com/
+
+=head2 C<-A> flag
+
+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.
+
+=head2 Enhanced Installation Directories
+
+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.
+
+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 Supported platforms
+
+=over 4
+
+=item *
+
+VM/ESA is now supported.
+
+=item *
+
+Siemens BS2000 is now supported under the POSIX Shell.
+
+=item *
+
+The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
+extension.
+
+=item *
+
+GNU/Hurd is now supported.
+
+=item *
+
+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
+
+=over 4
+
+=item *
+
+Perl now works with djgpp 2.02 (and 2.03 alpha).
+
+=item *
+
+Environment variable names are not converted to uppercase any more.
+
+=item *
+
+Incorrect exit codes from backticks have been fixed.
+
+=item *
+
+This port continues to use its own builtin globbing (not File::Glob).
+
+=back
+
+=head2 OS390 (OpenEdition MVS)
+
+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
+
+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
+
+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.
+
+The builtin XSUB functions in the Win32:: namespace are documented. See
+L<Win32>.
+
+$^X now contains the full path name of the running executable.
+
+A Win32::GetLongPathName() function is provided to complement
+Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
+
+POSIX::uname() is supported.
+
+system(1,...) now returns true process IDs rather than process
+handles. kill() accepts any real process id, rather than strictly
+return values from system(1,...).
+
+For better compatibility with Unix, C<kill(0, $pid)> can now be used to
+test whether a process exists.
+
+The C<Shell> module is supported.
+
+Better support for building Perl under command.com in Windows 95
+has been added.
+
+Scripts are read in binary mode by default to allow ByteLoader (and
+the filter mechanism in general) to work properly. For compatibility,
+the DATA filehandle will be set to text mode if a carriage return is
+detected at the end of the line containing the __END__ or __DATA__
+token; if not, the DATA filehandle will be left open in binary mode.
+Earlier versions always opened the DATA filehandle in text mode.
+
+The glob() operator is implemented via the C<File::Glob> extension,
+which supports glob syntax of the C shell. This increases the flexibility
+of the glob() operator, but there may be compatibility issues for
+programs that relied on the older globbing syntax. If you want to
+preserve compatibility with the older syntax, you might want to run
+perl with C<-MFile::DosGlob>. For details and compatibility information,
+see L<File::Glob>.
+
+=head1 Significant bug fixes
+
+=head2 <HANDLE> on empty files
+
+With C<$/> 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>.
+
+This means that the following will append "foo" to an empty file (it used
+to do nothing):
+
+ perl -0777 -pi -e 's/^/foo/' empty_file
+
+The behaviour of:
+
+ perl -pi -e 's/^/foo/' empty_file
+
+is unchanged (it continues to leave the file empty).
+
+=head2 C<eval '...'> improvements
+
+Line numbers (as reflected by caller() and most diagnostics) within
+C<eval '...'> were often incorrect where here documents were involved.
+This has been corrected.
+
+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.
+
+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.
+
+Parsing of here documents used to be flawed when they appeared as
+the replacement expression in C<eval 's/.../.../e'>. This has
+been fixed.
+
+=head2 All compilation errors are true errors
+
+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.
+
+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 "...">.
+
+=head2 Implicitly closed filehandles are safer
+
+Sometimes implicitly closed filehandles (as when they are localized,
+and Perl automatically closes them on exiting the scope) could
+inadvertently set $? or $!. This has been corrected.
+
+
+=head2 Behavior of list slices is more consistent
+
+When taking a slice of a literal list (as opposed to a slice of
+an array or hash), Perl used to return an empty list if the
+result happened to be composed of all undef values.
+
+The new behavior is to produce an empty list if (and only if)
+the original list was empty. Consider the following example:
+
+ @a = (1,undef,undef,2)[2,1,2];
+
+The old behavior would have resulted in @a having no elements.
+The new behavior ensures it has three undefined elements.
+
+Note in particular that the behavior of slices of the following
+cases remains unchanged:
+
+ @a = ()[1,2];
+ @a = (getpwent)[7,0];
+ @a = (anything_returning_empty_list())[2,1,2];
+ @a = @b[2,1,2];
+ @a = @c{'a','b','c'};
+
+See L<perldata>.
+
+=head2 C<(\$)> prototype and C<$foo{a}>
+
+A scalar reference prototype now correctly allows a hash or
+array element in that slot.
+
+=head2 C<goto &sub> and AUTOLOAD
+
+The C<goto &sub> construct works correctly when C<&sub> happens
+to be autoloaded.
+
+=head2 C<-bareword> allowed under C<use integer>
+
+The autoquoting of barewords preceded by C<-> did not work
+in prior versions when the C<integer> pragma was enabled.
+This has been fixed.
+
+=head2 Failures in DESTROY()
+
+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.
+
+=head2 Locale bugs fixed
+
+printf() and sprintf() previously reset the numeric locale
+back to the default "C" locale. This has been fixed.
+
+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.
+
+=head2 Memory leaks
+
+The C<eval 'return sub {...}'> construct could sometimes leak
+memory. This has been fixed.
+
+Operations that aren't filehandle constructors used to leak memory
+when used on invalid filehandles. This has been fixed.
+
+Constructs that modified C<@_> could fail to deallocate values
+in C<@_> and thus leak memory. This has been corrected.
+
+=head2 Spurious subroutine stubs after failed subroutine calls
+
+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 Taint failures under C<-U>
+
+When running in unsafe mode, taint violations could sometimes
+cause silent failures. This has been fixed.
+
+=head2 END blocks and the C<-c> switch
+
+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.
+
+See L<CHECK blocks> for how to run things when the compile phase ends.
+
+=head2 Potential to leak DATA filehandles
+
+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.
+
+This caveat is now better explained in the documentation.
+See L<perldata>.
+
+=head1 New or Changed Diagnostics
+
+=over 4
+
++=item (perhaps you forgot to load "%s"?)
++
++(F) This is an educated guess made in conjunction with the message
++"Can't locate object method \"%s\" via package \"%s\"". It often means
++that a method requires a package that has not been loaded.
++
+=item "%s" variable %s masks earlier declaration in same %s
+
+(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.
+
+=item "my sub" not yet implemented
+
+(F) Lexically scoped subroutines are not yet implemented. Don't try that
+yet.
+
+=item "our" variable %s redeclared
+
+(W misc) You seem to have already declared the same global once before in the
+current lexical scope.
+
+=item '!' allowed only after types %s
+
+(F) The '!' is allowed in pack() and unpack() only after certain types.
+See L<perlfunc/pack>.
+
+=item / cannot take a count
+
+(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>.
+
+=item / must be followed by a, A or Z
+
+(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 / must be followed by a*, A* or Z*
+
+(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 / must follow a numeric type
+
+(F) You had an unpack template that contained a '#',
+but this did not follow some numeric unpack specification.
+See L<perlfunc/pack>.
+
+=item /%s/: Unrecognized escape \\%c passed through
+
+(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.
+
+=item /%s/: Unrecognized escape \\%c in character class passed through
+
+(W regexp) 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"
+
+(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.
+
+=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 %s argument is not a HASH or ARRAY element
+
+(F) The argument to exists() must be a hash or array element, such as:
+
+ $foo{$bar}
+ $ref->{"susie"}[12]
+
+=item %s argument is not a HASH or ARRAY element or slice
+
+(F) The argument to delete() must be either a hash or array element, such as:
+
+ $foo{$bar}
+ $ref->{"susie"}[12]
+
+or a hash or array slice, such as:
+
+ @foo[$bar, $baz, $xyzzy]
+ @{$ref->[12]}{"susie", "queue"}
+
+=item %s argument is not a subroutine name
+
+(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 %s package attribute may clash with future reserved word: %s
+
+(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>.
+
+=item (in cleanup) %s
+
+(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.
+
+Failure of user callbacks dispatched using the C<G_KEEPERR> flag
+could also result in this warning. See L<perlcall/G_KEEPERR>.
+
+=item <> should be quotes
+
+(F) You wrote C<< require <file> >> when you should have written
+C<require 'file'>.
+
+=item Attempt to join self
+
+(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 Bad evalled substitution pattern
+
+(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 Bad realloc() ignored
+
+(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 Bareword found in conditional
+
+(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:
+
+ open FOO || die;
+
+It may also indicate a misspelled constant that has been interpreted
+as a bareword:
+
+ use constant TYPO => 1;
+ if (TYOP) { print "foo" }
+
+The C<strict> pragma is useful in avoiding such errors.
+
+=item Binary number > 0b11111111111111111111111111111111 non-portable
+
+(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.
+
+=item Bit vector size > 32 non-portable
+
+(W portable) Using bit vector sizes larger than 32 is non-portable.
+
+=item Buffer overflow in prime_env_iter: %s
+
+(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.
+
+=item Can't check filesystem of script "%s"
+
+(P) For some reason you can't check the filesystem of the script for nosuid.
+
+=item Can't declare class for non-scalar %s in "%s"
+
+(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 Can't declare %s in "%s"
+
+(F) Only scalar, array, and hash variables may be declared as "my" or
+"our" variables. They must have ordinary identifiers as names.
+
+=item Can't ignore signal CHLD, forcing to default
+
+(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.
+
+=item Can't modify non-lvalue subroutine call
+
+(F) Subroutines meant to be used in lvalue context should be declared as
+such, see L<perlsub/"Lvalue subroutines">.
+
+=item Can't read CRTL environ
+
+(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.
+
+=item Can't remove %s: %s, skipping file
+
+(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.
+
+=item Can't return %s from lvalue subroutine
+
+(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.
+
+=item Can't weaken a nonreference
+
+(F) You attempted to weaken something that was not a reference. Only
+references can be weakened.
+
+=item Character class [:%s:] unknown
+
+(F) The class in the character class [: :] syntax is unknown.
+See L<perlre>.
+
+=item Character class syntax [%s] belongs inside character classes
+
+(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.
+
+=item Constant is not %s reference
+
+(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>.
+
+=item constant(%s): %s
+
+(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 CORE::%s is not a keyword
+
+(F) The CORE:: namespace is reserved for Perl keywords.
+
+=item defined(@array) is deprecated
+
+(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 defined(%hash) is deprecated
+
+(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 Did not produce a valid header
+
+See Server error.
+
+=item (Did you mean "local" instead of "our"?)
+
+(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 Document contains no data
+
+See Server error.
+
+=item entering effective %s failed
+
+(F) While under the C<use filetest> pragma, switching the real and
+effective uids or gids failed.
+
+=item false [] range "%s" in regexp
+
+(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>.
+
+=item Filehandle %s opened only for output
+
+(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>.
+
+=item flock() on closed filehandle %s
+
+(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?
+
+=item Global symbol "%s" requires explicit package name
+
+(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 "::").
+
+=item Hexadecimal number > 0xffffffff non-portable
+
+(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.
+
+=item Ill-formed CRTL environ value "%s"
+
+(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.
+
+=item Ill-formed message in prime_env_iter: |%s|
+
+(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.
+
+=item Illegal binary digit %s
+
+(F) You used a digit other than 0 or 1 in a binary number.
+
+=item Illegal binary digit %s ignored
+
+(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.
+
+=item Illegal number of bits in vec
+
+(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).
+
+=item Integer overflow in %s number
+
+(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.
+
+=item Invalid %s attribute: %s
+
+The indicated attribute for a subroutine or variable was not recognized
+by Perl or by a user-supplied handler. See L<attributes>.
+
+=item Invalid %s attributes: %s
+
+The indicated attributes for a subroutine or variable were not recognized
+by Perl or by a user-supplied handler. See L<attributes>.
+
+=item invalid [] range "%s" in regexp
+
+The offending range is now explicitly displayed.
+
+=item Invalid separator character %s in attribute list
+
+(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>.
+
+=item Invalid separator character %s in subroutine attribute list
-=head1 Improved Documentation
+(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.
-=head1 Performance enhancements
+=item leaving effective %s failed
-=head1 Installation and Configuration Improvements
+(F) While under the C<use filetest> pragma, switching the real and
+effective uids or gids failed.
-=head1 Platform specific changes
+=item Lvalue subs returning %s not implemented yet
-=head1 Significant bug fixes
+(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">.
-=head1 New or Changed Diagnostics
+=item Method %s not permitted
-=over 4
+See Server error.
-=item (perhaps you forgot to load "%s"?)
+=item Missing %sbrace%s on \N{}
-(F) This is an educated guess made in conjunction with the message
-"Can't locate object method \"%s\" via package \"%s\"". It often means
-that a method requires a package that has not been loaded.
+(F) Wrong syntax of character name literal C<\N{charname}> within
+double-quotish context.
+
+=item Missing command in piped open
+
+(W pipe) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
+construction, but the command was missing or blank.
+
+=item Missing name in "my sub"
+
+(F) The reserved syntax for lexically scoped subroutines requires that they
+have a name with which they can be found.
+
+=item No %s specified for -%c
+
+(F) The indicated command line switch needs a mandatory argument, but
+you haven't specified one.
+
+=item No package name allowed for variable %s in "our"
+
+(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 No space allowed after -%c
+
+(F) The argument to the indicated command line switch must follow immediately
+after the switch, without intervening spaces.
+
+=item no UTC offset information; assuming local time is UTC
+
+(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.
+
+=item Octal number > 037777777777 non-portable
+
+(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.
+
+See also L<perlport> for writing portable code.
+
+=item panic: del_backref
+
+(P) Failed an internal consistency check while trying to reset a weak
+reference.
+
+=item panic: kid popen errno read
+
+(F) forked child returned an incomprehensible message about its errno.
+
+=item panic: magic_killbackrefs
+
+(P) Failed an internal consistency check while trying to reset all weak
+references to an object.
+
+=item Parentheses missing around "%s" list
+
+(W parenthesis) You said something like
+
+ my $foo, $bar = @_;
+
+when you meant
+
+ my ($foo, $bar) = @_;
+
+Remember that "my", "our", and "local" bind tighter than comma.
+
+=item Possible Y2K bug: %s
+
+(W y2k) You are concatenating the number 19 with another number, which
+could be a potential Year 2000 problem.
+
+=item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
+
+(W deprecated) You have written somehing like this:
+
+ sub doit
+ {
+ use attrs qw(locked);
+ }
+
+You should use the new declaration syntax instead.
+
+ sub doit : locked
+ {
+ ...
+
+The C<use attrs> pragma is now obsolete, and is only provided for
+backward-compatibility. See L<perlsub/"Subroutine Attributes">.
+
+
+=item Premature end of script headers
+
+See Server error.
+
+=item Repeat count in pack overflows
+
+(F) You can't specify a repeat count so large that it overflows
+your signed integers. See L<perlfunc/pack>.
+
+=item Repeat count in unpack overflows
+
+(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
+
+(S) An internal routine called realloc() on something that had already
+been freed.
+
+=item Reference is already weak
+
+(W misc) You have attempted to weaken a reference that is already weak.
+Doing so has no effect.
+
+=item setpgrp can't take arguments
+
+(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.
+
+=item Strange *+?{} on zero-length expression
+
+(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}/>.
+
+=item switching effective %s is not implemented
+
+(F) While under the C<use filetest> pragma, we cannot switch the
+real and effective uids or gids.
+
+=item This Perl can't reset CRTL environ elements (%s)
+
+=item This Perl can't set CRTL environ elements (%s=%s)
+
+(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.
+
+=item Too late to run %s block
+
+(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.
+
+=item Unknown open() mode '%s'
+
+(F) The second argument of 3-argument open() is not among the list
+of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
+C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
+
+=item Unknown process %x sent message to prime_env_iter: %s
+
+(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.
+
+=item Unrecognized escape \\%c passed through
+
+(W misc) You used a backslash-character combination which is not recognized
+by Perl. The character was understood literally.
+
+=item Unterminated attribute parameter in attribute list
+
+(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>.
+
+=item Unterminated attribute list
+
+(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 Unterminated attribute parameter in subroutine attribute list
+
+(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 Unterminated subroutine attribute list
+
+(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 Value of CLI symbol "%s" too long
+
+(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.
+
+=item Version number must be a constant number
+
+(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.
=back
projects / p5sagit/p5-mst-13.2.git / commitdiff