3 perldelta - what's new for perl v5.6 (as of v5.005_62)
7 This is an unsupported alpha release, meant for intrepid Perl developers
8 only. The included sources may not even build correctly on some platforms.
9 Subscribing to perl5-porters is the best way to monitor and contribute
10 to the progress of development releases (see www.perl.org for info).
12 This document describes differences between the 5.005 release and this one.
14 =head1 Incompatible Changes
16 =head2 Perl Source Incompatibilities
18 Beware that any new warnings that have been added or enhanced old
19 warnings are B<not> considered incompatible changes.
21 Since all new warnings must be explicitly requested via the C<-w>
22 switch or the C<warnings> pragma, it is ultimately the programmer's
23 responsibility to ensure that warnings are enabled judiciously.
27 =item STOP is a new keyword
29 In addition to C<BEGIN>, C<INIT> and C<END>, subroutines named
30 C<STOP> are now special. They are queued up for execution at the
31 end of compilation, and cannot be called directly.
33 =item Treatment of list slices of undef has changed
35 When taking a slice of a literal list (as opposed to a slice of
36 an array or hash), Perl used to return an empty list if the
37 result happened to be composed of all undef values.
39 The new behavior is to produce an empty list if (and only if)
40 the original list was empty. Consider the following example:
42 @a = (1,undef,undef,2)[2,1,2];
44 The old behavior would have resulted in @a having no elements.
45 The new behavior ensures it has three undefined elements.
47 Note in particular that the behavior of slices of the following
48 cases remains unchanged:
52 @a = (anything_returning_empty_list())[2,1,2];
58 =item Possibly changed pseudo-random number generator
60 In 5.005_0x and earlier, perl's rand() function used the C library
61 rand(3) function. As of 5.005_52, Configure tests for drand48(),
62 random(), and rand() (in that order) and picks the first one it finds.
63 Perl programs that depend on reproducing a specific set of pseudo-random
64 numbers will now likely produce different output. You can use
65 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
67 =item Hashing function for hash keys has changed
69 Perl hashes are not order preserving. The apparently random order
70 encountered when iterating on the contents of a hash is determined
71 by the hashing algorithm used. To improve the distribution of lower
72 bits in the hashed value, the algorithm has changed slightly as of
73 5.005_52. When iterating over hashes, this may yield a random order
74 that is B<different> from that of previous versions.
76 =item C<undef> fails on read only values
78 Using the C<undef> operator on a readonly value (such as $1) has
79 the same effect as assigning C<undef> to the readonly value--it
82 =item Close-on-exec bit may be set on pipe() handles
84 On systems that support a close-on-exec flag on filehandles, the
85 flag will be set for any handles created by pipe(), if that is
86 warranted by the value of $^F that may be in effect. Earlier
87 versions neglected to set the flag for handles created with
88 pipe(). See L<perlfunc/pipe> and L<perlvar/$^F>.
90 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
92 Perl 5.004 deprecated the interpretation of C<$$1> and
93 similar within interpolated strings to mean C<$$ . "1">,
96 In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
98 =item values(%h) and C<\(%h)> operate on aliases to values, not copies
100 each(), values() and hashes in a list context return the actual
101 values in the hash, instead of copies (as they used to in earlier
102 versions). Typical idioms for using these constructs copy the
103 returned values, but this can make a significant difference when
104 creating references to the returned values.
106 Keys in the hash are still returned as copies when iterating on
109 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
111 vec() generates a run-time error if the BITS argument is not
112 a valid power-of-two integer.
114 =item Text of some diagnostic output has changed
116 Most references to internal Perl operations in diagnostics
117 have been changed to be more descriptive. This may be an
118 issue for programs that may incorrectly rely on the exact
119 text of diagnostics for proper functioning.
121 =item C<%@> has been removed
123 The undocumented special variable C<%@> that used to accumulate
124 "background" errors (such as those that happen in DESTROY())
125 has been removed, because it could potentially result in memory
128 =item Parenthesized not() behaves like a list operator
130 The C<not> operator now falls under the "if it looks like a function,
131 it behaves like a function" rule.
133 As a result, the parenthesized form can be used with C<grep> and C<map>.
134 The following construct used to be a syntax error before, but it works
137 grep not($_), @things;
139 On the other hand, using C<not> with a literal list slice may not
140 work. The following previously allowed construct:
142 print not (1,2,3)[0];
144 needs to be written with additional parentheses now:
146 print not((1,2,3)[0]);
148 The behavior remains unaffected when C<not> is not followed by parentheses.
152 =head2 C Source Incompatibilities
156 =item C<PERL_POLLUTE>
158 Release 5.005 grandfathered old global symbol names by providing preprocessor
159 macros for extension source compatibility. As of release 5.6, these
160 preprocessor definitions are not available by default. You need to explicitly
161 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
162 extensions still using the old symbols, this option can be
163 specified via MakeMaker:
165 perl Makefile.PL POLLUTE=1
167 =item C<PERL_IMPLICIT_CONTEXT>
169 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
170 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
171 intended to be enabled by users at this time.
173 This new build option provides a set of macros for all API functions
174 such that an implicit interpreter/thread context argument is passed to
175 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
176 amounts to a macro invocation that actually translates to something like
177 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
178 to not have any significant source compatibility issues, the difference
179 between a macro and a real function call will need to be considered.
181 This means that there B<is> a source compatibility issue as a result of
182 this if your extensions attempt to use pointers to any of the Perl API
185 Note that the above issue is not relevant to the default build of
186 Perl, whose interfaces continue to match those of prior versions
187 (but subject to the other options described here).
189 See L<perlguts/"The Perl API"> for detailed information on the
190 ramifications of building Perl using this option.
192 =item C<PERL_POLLUTE_MALLOC>
194 Enabling Perl's malloc in release 5.005 and earlier caused
195 the namespace of system versions of the malloc family of functions to
196 be usurped by the Perl versions, since by default they used the
199 Besides causing problems on platforms that do not allow these functions to
200 be cleanly replaced, this also meant that the system versions could not
201 be called in programs that used Perl's malloc. Previous versions of Perl
202 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
203 EMBEDMYMALLOC preprocessor definitions.
205 As of release 5.6, Perl's malloc family of functions have default names
206 distinct from the system versions. You need to explicitly compile perl with
207 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
208 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
211 Note that these functions do B<not> constitute Perl's memory allocation API.
212 See L<perlguts/"Memory Allocation"> for further information about that.
216 =head2 Compatible C Source API Changes
220 =item C<PATCHLEVEL> is now C<PERL_VERSION>
222 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
223 are now available by default from perl.h, and reflect the base revision,
224 patchlevel, and subversion respectively. C<PERL_REVISION> had no
225 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
226 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
228 The new names cause less pollution of the B<cpp> namespace and reflect what
229 the numbers have come to stand for in common practice. For compatibility,
230 the old names are still supported when F<patchlevel.h> is explicitly
231 included (as required before), so there is no source incompatibility
234 =item Support for C++ exceptions
236 change#3386, also needs perlguts documentation
237 [TODO - Chip Salzenberg <chip@perlsupport.com>]
241 =head2 Binary Incompatibilities
243 The default build of this release is binary compatible with the 5.005
244 release or its maintenance versions.
246 The usethreads or usemultiplicity builds are B<not> binary compatible
247 with the corresponding builds in 5.005.
249 =head1 Installation and Configuration Improvements
251 =head2 New Configure flags
253 The following new flags may be enabled on the Configure command line
254 by running Configure with C<-Dflag>.
262 =head2 -Dusethreads and -Duse64bits now more daring
264 The Configure options enabling the use of threads and the use of
265 64-bitness are now more daring in the sense that they no more have
266 an explicit list of operating systems of known threads/64-bit
267 capabilities. In other words: if your operating system has the
268 necessary APIs, you should be able just to go ahead and use them.
269 See also L<"64-bit support">.
273 Some platforms have "long doubles", floating point numbers of even
274 larger range than ordinary "doubles". To enable using long doubles for
275 Perl's scalars, use -Duselongdouble.
279 You can enable both -Duse64bits and -Dlongdouble by -Dusemorebits.
280 See also L<"64-bit support">.
282 =head2 -Duselargefiles
284 Some platforms support large files, files larger than two gigabytes.
285 See L<"Large file support"> for more information.
287 =head2 installusrbinperl
289 You can use "Configure -Uinstallusrbinperl" which causes installperl
290 to skip installing perl also as /usr/bin/perl. This is useful if you
291 prefer not to modify /usr/bin for some reason or another but harmful
292 because many scripts assume to find Perl in /usr/bin/perl.
296 You can use "Configure -Dusesocks" which causes Perl to probe
297 for the SOCKS (v5, not v4) proxy protocol library,
298 http://www.socks.nec.com/
302 You can "post-edit" the Configure variables using the Configure C<-A>
303 flag. The editing happens immediately after the platform specific
304 hints files have been processed but before the actual configuration
305 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
307 =head2 Enhanced Installation Directories
309 The installation structure has been enriched to improve the support for
310 maintaining multiple versions of perl, to provide locations for
311 vendor-supplied modules and scripts, and to ease maintenance of
312 locally-added modules and scripts. See the section on Installation
313 Directories in the INSTALL file for complete details. For most users
314 building and installing from source, the defaults should be fine.
318 =head2 Unicode and UTF-8 support
320 Perl can optionally use UTF-8 as its internal representation for character
321 strings. The C<utf8> pragma enables this support in the current lexical
322 scope. See L<utf8> for more information.
324 =head2 Interpreter threads
326 WARNING: This is an experimental feature in a pre-alpha state. Use
329 Perl 5.005_63 introduces the beginnings of support for running multiple
330 interpreters concurrently in different threads. In conjunction with
331 the perl_clone() API call, which can be used to selectively duplicate
332 the state of any given interpreter, it is possible to compile a
333 piece of code once in an interpreter, clone that interpreter
334 one or more times, and run all the resulting interpreters in distinct
337 On Windows, this feature is used to emulate fork() at the interpreter
338 level. See L<perlfork>.
340 This feature is still in evolution. It is eventually meant to be used
341 to selectively clone a subroutine and data reachable from that
342 subroutine in a separate interpreter and run the cloned subroutine
343 in a separate thread. Since there is no shared data between the
344 interpreters, little or no locking will be needed (unless parts of
345 the symbol table are explicitly shared). This is obviously intended
346 to be an easy-to-use replacement for the existing threads support.
348 Support for cloning interpreters must currently be manually enabled
349 by defining the cpp macro USE_ITHREADS on non-Windows platforms.
350 (See win32/Makefile for how to enable it on Windows.) The resulting
351 perl executable will be functionally identical to one that was built
352 without USE_ITHREADS, but the perl_clone() API call will only be
353 available in the former.
355 USE_ITHREADS enables Perl source code changes that provide a clear
356 separation between the op tree and the data it operates with. The
357 former is considered immutable, and can therefore be shared between
358 an interpreter and all of its clones, while the latter is considered
359 local to each interpreter, and is therefore copied for each clone.
361 Note that building Perl with the -Dusemultiplicity Configure option
362 is adequate if you wish to run multiple B<independent> interpreters
363 concurrently in different threads. USE_ITHREADS only needs to be
364 enabled if you wish to obtain access to perl_clone() and cloned
367 [XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
370 =head2 Lexically scoped warning categories
372 You can now control the granularity of warnings emitted by perl at a finer
373 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
376 =head2 Lvalue subroutines
378 WARNING: This is an experimental feature.
381 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
382 Tuomas Lukka <lukka@fas.harvard.edu>)]
384 =head2 "our" declarations
386 An "our" declaration introduces a value that can be best understood
387 as a lexically scoped symbolic alias to a global variable in the
388 current package. This is mostly useful as an alternative to the
389 C<vars> pragma, but also provides the opportunity to introduce
390 typing and other attributes for such variables. See L<perlfunc/our>.
392 =head2 Weak references
394 WARNING: This is an experimental feature.
396 change#3385, also need perlguts documentation
398 [TODO - Tuomas Lukka <lukka@fas.harvard.edu>]
400 =head2 File globbing implemented internally
402 WARNING: This is currently an experimental feature. Interfaces and
403 implementation are likely to change.
405 Perl now uses the File::Glob implementation of the glob() operator
406 automatically. This avoids using an external csh process and the
407 problems associated with it.
409 =head2 Binary numbers supported
411 Binary numbers are now supported as literals, in s?printf formats, and
415 printf "The answer is: %b\n", oct("0b101010");
417 =head2 Some arrows may be omitted in calls through references
419 Perl now allows the arrow to be omitted in many constructs
420 involving subroutine calls through references. For example,
421 C<$foo[10]->('foo')> may now be written C<$foo[10]('foo')>.
422 This is rather similar to how the arrow may be omitted from
423 C<$foo[10]->{'foo'}>. Note however, that the arrow is still
424 required for C<foo(10)->('bar')>.
426 =head2 syswrite() ease-of-use
428 The length argument of C<syswrite()> has become optional.
430 =head2 Filehandles can be autovivified
432 Similar to how constructs such as C<$x->[0]> autovivify a reference,
433 open() now autovivifies a filehandle if the first argument is an
434 uninitialized variable. This allows the constructs C<open(my $fh, ...)> and
435 C<open(local $fh,...)> to be used to create filehandles that will
436 conveniently be closed automatically when the scope ends, provided there
437 are no other references to them. This largely eliminates the need for
438 typeglobs when opening filehandles that must be passed around, as in the
443 or die "Can't open '@_': $!";
448 my $f = myopen("</etc/motd");
450 # $f implicitly closed here
453 [TODO - this idiom needs more pod penetration]
455 =head2 64-bit support
457 All platforms that have 64-bit integers either (a) natively as longs
458 or ints (b) via special compiler flags (c) using long long are able to
459 use "quads" (64-integers) as follows:
465 constants (decimal, hexadecimal, octal, binary) in the code
469 arguments to oct() and hex()
473 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
481 pack() and unpack() "q" and "Q" formats
485 in basic arithmetics: + - * / %
489 vec() (but see the below note about bit arithmetics)
493 Note that unless you have the case (a) you will have to configure
494 and compile Perl using the -Duse64bits Configure flag.
496 Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
497 64-bit clean, they are explictly forced to be 32-bit. Bit arithmetics
498 for bit vectors (created by vec()) are not limited in their width.
500 Last but not least: note that due to Perl's habit of always using
501 floating point numbers the quads are still not true integers.
502 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
503 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
504 are silently promoted to floating point numbers, after which they will
505 start losing precision (their lower digits).
507 =head2 Large file support
509 If you have filesystems that support "large files" (files larger than
510 2 gigabytes), you may now also be able to create and access them from
511 Perl. You have to use Configure -Duselargefiles. Turning on the
512 large file support turns on also the 64-bit support, for obvious reasons.
514 Note that in addition to requiring a proper file system to do large
515 files you may also need to adjust your per-process (or your
516 per-system, or per-process-group, or per-user-group) maximum filesize
517 limits before running Perl scripts that try to handle large files,
518 especially if you intend to write such files.
520 Finally, in addition to your process/process group maximum filesize
521 limits, you may have quota limits on your filesystems that stop you
522 (your user id or your user group id) from using large files.
524 Adjusting your process/user/group/file system/operating system limits
525 is outside the scope of Perl core language. For process limits, you
526 may try increasing the limits using your shell's limits/limit/ulimit
527 command before running Perl. The BSD::Resource extension (not
528 included with the standard Perl distribution) may also be of use, it
529 offers the getrlimit/setrlimit interface that can be used to adjust
530 process resource usage limits, including the maximum filesize limit.
534 In some systems you may be able to use long doubles to enhance the
535 range of precision of your double precision floating point numbers
536 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
537 this support (if it is available).
541 You can Configure -Dusemorebits to turn on both the 64-bit support
542 and the long double support.
544 =head2 Enhanced support for sort() subroutines
546 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
547 now be used as sort subroutines. In either case, the two elements to
548 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
550 For unprototyped sort subroutines, the historical behavior of passing
551 the elements to be compared as the global variables $a and $b remains
554 =head2 Better syntax checks on parenthesized unary operators
558 print defined(&foo,&bar,&baz);
559 print uc("foo","bar","baz");
562 used to be accidentally allowed in earlier versions, and produced
563 unpredictable behaviour. Some produced ancillary warnings
564 when used in this way; others silently did the wrong thing.
566 The parenthesized forms of most unary operators that expect a single
567 argument now ensure that they are not called with more than one
568 argument, making the cases shown above syntax errors. The usual
571 print defined &foo, &bar, &baz;
572 print uc "foo", "bar", "baz";
575 remains unchanged. See L<perlop>.
577 =head2 POSIX character class syntax [: :] supported
579 For example to match alphabetic characters use /[[:alpha:]]/.
580 See L<perlre> for details.
582 =head2 Improved C<qw//> operator
584 The C<qw//> operator is now evaluated at compile time into a true list
585 instead of being replaced with a run time call to C<split()>. This
586 removes the confusing misbehaviour of C<qw//> in scalar context, which
587 had inherited that behaviour from split().
591 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
593 now correctly prints "3|a", instead of "2|a".
595 =head2 pack() format 'Z' supported
597 The new format type 'Z' is useful for packing and unpacking null-terminated
598 strings. See L<perlfunc/"pack">.
600 =head2 pack() format modifier '!' supported
602 The new format type modifier '!' is useful for packing and unpacking
603 native shorts, ints, and longs. See L<perlfunc/"pack">.
605 =head2 pack() and unpack() support counted strings
607 The template character '/' can be used to specify a counted string
608 type to be packed or unpacked. See L<perlfunc/"pack">.
610 =head2 Comments in pack() templates
612 The '#' character in a template introduces a comment up to
613 end of the line. This facilitates documentation of pack()
616 =head2 $^X variables may now have names longer than one character
618 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
619 error. Now variable names that begin with a control character may be
620 arbitrarily long. However, for compatibility reasons, these variables
621 I<must> be written with explicit braces, as C<${^XY}> for example.
622 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
623 than one control character, such as C<${^XY^Z}>, are illegal.
625 The old syntax has not changed. As before, `^X' may be either a
626 literal control-X character or the two-character sequence `caret' plus
627 `X'. When braces are omitted, the variable name stops after the
628 control character. Thus C<"$^XYZ"> continues to be synonymous with
629 C<$^X . "YZ"> as before.
631 As before, lexical variables may not have names beginning with control
632 characters. As before, variables whose names begin with a control
633 character are always forced to be in package `main'. All such variables
634 are reserved for future extensions, except those that begin with
635 C<^_>, which may be used by user programs and are guaranteed not to
636 acquire special meaning in any future version of Perl.
638 =head2 C<use attrs> implicit in subroutine attributes
640 Formerly, if you wanted to mark a subroutine as being a method call or
641 as requiring an automatic lock() when it is entered, you had to declare
642 that with a C<use attrs> pragma in the body of the subroutine.
643 That can now be accomplished with a declaration syntax, like this:
645 sub mymethod : locked, method ;
647 sub mymethod : locked, method {
651 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
652 with the stubs they provide. See L<attributes>.
654 =head2 Regular expression improvements
656 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
657 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
659 =head2 Overloading improvements
662 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
664 =head2 open() with more than two arguments
666 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
668 =head2 Support for interpolating named characters
671 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
673 =head2 Experimental support for user-hooks in @INC
675 [TODO - Ken Fox <kfox@ford.com>]
677 =head2 C<require> and C<do> may be overridden
679 C<require> and C<do 'file'> operations may be overridden locally
680 by importing subroutines of the same name into the current package
681 (or globally by importing them into the CORE::GLOBAL:: namespace).
682 Overriding C<require> will also affect C<use>, provided the override
683 is visible at compile-time.
684 See L<perlsub/"Overriding Built-in Functions">.
686 =head2 New variable $^C reflects C<-c> switch
688 C<$^C> has a boolean value that reflects whether perl is being run
689 in compile-only mode (i.e. via the C<-c> switch). Since
690 BEGIN blocks are executed under such conditions, this variable
691 enables perl code to determine whether actions that make sense
692 only during normal running are warranted. See L<perlvar>.
696 Arbitrary code can be queued for execution when Perl has finished
697 parsing the program (i.e. when the compile phase ends) using STOP
698 blocks. These behave similar to END blocks, except for being
699 called at the end of compilation rather than at the end of execution.
701 =head2 Optional Y2K warnings
703 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
704 it emits optional warnings when concatenating the number 19
707 This behavior must be specifically enabled when running Configure.
708 See L<INSTALL> and L<README.Y2K>.
710 =head1 Significant bug fixes
712 =head2 E<lt>HANDLEE<gt> on empty files
714 With C<$/> set to C<undef>, slurping an empty file returns a string of
715 zero length (instead of C<undef>, as it used to) the first time the
716 HANDLE is read. Further reads yield C<undef>.
718 This means that the following will append "foo" to an empty file (it used
721 perl -0777 -pi -e 's/^/foo/' empty_file
725 perl -pi -e 's/^/foo/' empty_file
727 is unchanged (it continues to leave the file empty).
729 =head2 C<eval '...'> improvements
731 Line numbers (as reflected by caller() and most diagnostics) within
732 C<eval '...'> were often incorrect when here documents were involved.
733 This has been corrected.
735 Lexical lookups for variables appearing in C<eval '...'> within
736 functions that were themselves called within an C<eval '...'> were
737 searching the wrong place for lexicals. The lexical search now
738 correctly ends at the subroutine's block boundary.
740 Parsing of here documents used to be flawed when they appeared as
741 the replacement expression in C<eval 's/.../.../e'>. This has
744 =head2 All compilation errors are true errors
746 Some "errors" encountered at compile time were by neccessity
747 generated as warnings followed by eventual termination of the
748 program. This enabled more such errors to be reported in a
749 single run, rather than causing a hard stop at the first error
750 that was encountered.
752 The mechanism for reporting such errors has been reimplemented
753 to queue compile-time errors and report them at the end of the
754 compilation as true errors rather than as warnings. This fixes
755 cases where error messages leaked through in the form of warnings
756 when code was compiled at run time using C<eval STRING>, and
757 also allows such errors to be reliably trapped using __DIE__ hooks.
759 =head2 Automatic flushing of output buffers
761 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
762 of all files opened for output when the operation
763 was attempted. This mostly eliminates confusing
764 buffering mishaps suffered by users unaware of how Perl internally
767 =head2 Better diagnostics on meaningless filehandle operations
769 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
770 are compile time errors. Attempting to read from filehandles that
771 were opened only for writing will now produce warnings (just as
772 writing to read-only filehandles does).
774 =head2 Where possible, buffered data discarded from duped input filehandle
776 C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
777 was previously read and buffered in C<OLD> before duping the handle.
778 On platforms where doing this is allowed, the next read operation
779 on C<NEW> will return the same data as the corresponding operation
780 on C<OLD>. Formerly, it would have returned the data from the start
781 of the following disk block instead.
783 =head2 system(), backticks and pipe open now reflect exec() failure
785 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
786 etc., are implemented via fork() and exec(). When the underlying
787 exec() fails, earlier versions did not report the error properly,
788 since the exec() happened to be in a different process.
790 The child process now communicates with the parent about the
791 error in launching the external command, which allows these
792 constructs to return with their usual error value and set $!.
794 =head2 Implicitly closed filehandles are safer
796 Sometimes implicitly closed filehandles (as when they are localized,
797 and Perl automatically closes them on exiting the scope) could
798 inadvertently set $? or $!. This has been corrected.
800 =head2 C<(\$)> prototype and C<$foo{a}>
802 An scalar reference prototype now correctly allows a hash or
803 array element in that slot.
805 =head2 Pseudo-hashes work better
807 Dereferencing some types of reference values in a pseudo-hash,
808 such as C<$ph->{foo}[1]>, was accidentally disallowed. This has
811 When applied to a pseudo-hash element, exists() now reports whether
812 the specified value exists, not merely if the key is valid.
814 =head2 C<goto &sub> and AUTOLOAD
816 The C<goto &sub> construct works correctly when C<&sub> happens
819 =head2 C<-bareword> allowed under C<use integer>
821 The autoquoting of barewords preceded by C<-> did not work
822 in prior versions when the C<integer> pragma was enabled.
825 =head2 Boolean assignment operators are legal lvalues
827 Constructs such as C<($a ||= 2) += 1> are now allowed.
829 =head2 C<sort $coderef @foo> allowed
831 sort() did not accept a subroutine reference as the comparison
832 function in earlier versions. This is now permitted.
834 =head2 Failures in DESTROY()
836 When code in a destructor threw an exception, it went unnoticed
837 in earlier versions of Perl, unless someone happened to be
838 looking in $@ just after the point the destructor happened to
839 run. Such failures are now visible as warnings when warnings are
842 =head2 Locale bugs fixed
844 printf() and sprintf() previously reset the numeric locale
845 back to the default "C" locale. This has been fixed.
847 Numbers formatted according to the local numeric locale
848 (such as using a decimal comma instead of a decimal dot) caused
849 "isn't numeric" warnings, even while the operations accessing
850 those numbers produced correct results. The warnings are gone.
854 The C<eval 'return sub {...}'> construct could sometimes leak
855 memory. This has been fixed.
857 Operations that aren't filehandle constructors used to leak memory
858 when used on invalid filehandles. This has been fixed.
860 Constructs that modified C<@_> could fail to deallocate values
861 in C<@_> and thus leak memory. This has been corrected.
863 =head2 Spurious subroutine stubs after failed subroutine calls
865 Perl could sometimes create empty subroutine stubs when a
866 subroutine was not found in the package. Such cases stopped
867 later method lookups from progressing into base packages.
868 This has been corrected.
870 =head2 Consistent numeric conversions
873 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
875 =head2 Taint failures under C<-U>
877 When running in unsafe mode, taint violations could sometimes
878 cause silent failures. This has been fixed.
880 =head2 END blocks and the C<-c> switch
882 Prior versions used to run BEGIN B<and> END blocks when Perl was
883 run in compile-only mode. Since this is typically not the expected
884 behavior, END blocks are not executed anymore when the C<-c> switch
887 See L<STOP blocks> for how to run things when the compile phase ends.
889 =head2 Potential to leak DATA filehandles
891 Using the C<__DATA__> token creates an implicit filehandle to
892 the file that contains the token. It is the program's
893 responsibility to close it when it is done reading from it.
895 This caveat is now better explained in the documentation.
898 =head2 Diagnostics follow STDERR
900 Diagnostic output now goes to whichever file the C<STDERR> handle
901 is pointing at, instead of always going to the underlying C runtime
904 =head2 Other fixes for better diagnostics
906 Line numbers are no longer suppressed (under most likely circumstances)
907 during the global destruction phase.
909 Diagnostics emitted from code running in threads other than the main
910 thread are now accompanied by the thread ID.
912 Embedded null characters in diagnostics now actually show up. They
913 used to truncate the message in prior versions.
915 $foo::a and $foo::b are now exempt from "possible typo" warnings only
916 if sort() is encountered in package foo.
918 Unrecognized alphabetic escapes encountered when parsing quote
919 constructs now generate a warning, since they may take on new
920 semantics in later versions of Perl.
922 =head1 Performance enhancements
924 =head2 Simple sort() using { $a <=> $b } and the like are optimized
926 Many common sort() operations using a simple inlined block are now
927 optimized for faster performance.
929 =head2 Optimized assignments to lexical variables
931 Certain operations in the RHS of assignment statements have been
932 optimized to directly set the lexical variable on the LHS,
933 eliminating redundant copying overheads.
935 =head2 Method lookups optimized
937 [TODO - Chip Salzenberg <chip@perlsupport.com>]
939 =head2 Faster mechanism to invoke XSUBs
942 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
944 =head2 Perl_malloc() improvements
947 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
949 =head2 Faster subroutine calls
951 Minor changes in how subroutine calls are handled internally
952 provide marginal improvements in performance.
954 =head1 Platform specific changes
956 =head2 Additional supported platforms
962 VM/ESA is now supported.
966 Siemens BS2000 is now supported under the POSIX Shell.
970 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
975 GNU/Hurd is now supported.
979 Rhapsody is now supported.
983 EPOC is is now supported (on Psion 5).
993 Perl now works with djgpp 2.02 (and 2.03 alpha).
997 Environment variable names are not converted to uppercase any more.
1001 Wrong exit code from backticks now fixed.
1005 This port is still using its own builtin globbing.
1011 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1015 [TODO - Charles Bailey <bailey@newman.upenn.edu>]
1019 Site library searches failed to look for ".../site/5.XXX/lib"
1020 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1022 When given a pathname that consists only of a drivename, such
1023 as C<A:>, opendir() and stat() now use the current working
1024 directory for the drive rather than the drive root.
1026 The builtin XSUB functions in the Win32:: namespace are
1027 documented. See L<Win32>.
1029 $^X now contains the full path name of the running executable.
1031 A Win32::GetLongPathName() function is provided to complement
1032 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1034 POSIX::uname() is supported.
1036 system(1,...) now returns true process IDs rather than process
1037 handles. kill() accepts any real process id, rather than strictly
1038 return values from system(1,...).
1040 The C<Shell> module is supported.
1042 Rudimentary support for building under command.com in Windows 95
1053 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1057 IO constants (SEEK_*, _IO*).
1061 Directory-related IO methods (new, read, close, rewind, tied delete).
1063 =item lib/io_multihomed
1065 INET sockets with multi-homed hosts.
1077 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1081 File test operators.
1085 Verify operations that access pad objects (lexicals and temporaries).
1089 =head1 Modules and Pragmata
1097 While used internally by Perl as a pragma, this module also
1098 provides a way to fetch subroutine and variable attributes.
1103 The Perl Compiler suite has been extensively reworked for this
1106 [TODO - Vishal Bhatia <vishal@gol.com>,
1107 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1111 The ByteLoader is a dedicated extension to generate and run
1112 Perl bytecode. See L<ByteLoader>.
1116 References can now be used. See L<constant>.
1121 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1125 A C<Maxdepth> setting can be specified to avoid venturing
1126 too deeply into deep data structures. See L<Data::Dumper>.
1128 Dumping C<qr//> objects works correctly.
1132 C<DB> is an experimental module that exposes a clean abstraction
1133 to Perl's debugging API.
1137 [TODO - Paul Marquess <paul.marquess@bt.com>]
1141 Devel::DProf, a Perl source code profiler has been added. See
1142 L<Devel::DProf> and L<dprofpp>.
1146 The Dumpvalue module provides screen dumps of Perl data.
1150 Overall, Benchmark results exhibit lower average error and better timing
1153 You can now run tests for I<n> seconds instead of guessing the right
1154 number of tests to run: e.g. timethese(-5, ...) will run each
1155 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1156 means "for at least 3 CPU seconds". The output format has also
1157 changed. For example:
1159 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1161 will now output something like this:
1163 Benchmark: running a, b, each for at least 5 CPU seconds...
1164 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1165 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1167 New features: "each for at least N CPU seconds...", "wallclock secs",
1168 and the "@ operations/CPU second (n=operations)".
1170 timethese() now returns a reference to a hash of Benchmark objects containing
1171 the test results, keyed on the names of the tests.
1173 timethis() now returns the iterations field in the Benchmark result object
1176 timethese(), timethis(), and the new cmpthese() (see below) can also take
1177 a format specifier of 'none' to suppress output.
1179 A new function countit() is just like timeit() except that it takes a
1180 TIME instead of a COUNT.
1182 A new function cmpthese() prints a chart comparing the results of each test
1183 returned from a timethese() call. For each possible pair of tests, the
1184 percentage speed difference (iters/sec or seconds/iter) is shown.
1186 For other details, see L<Benchmark>.
1190 The Devel::Peek module provides access to the internal representation
1191 of Perl variables and data. It is a data debugging tool for the XS programmer.
1193 =item ExtUtils::MakeMaker
1195 change#4135, also needs docs in module pod
1196 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1200 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1201 large (more than 4G) file access (64-bit support is not yet
1202 working, though, so no need to get overly excited), Free/Net/OpenBSD
1203 locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and
1204 O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR.
1208 A compare_text() function has been added, which allows custom
1209 comparison functions. See L<File::Compare>.
1213 File::Find now works correctly when the wanted() function is either
1214 autoloaded or is a symbolic reference.
1216 A bug that caused File::Find to lose track of the working directory
1217 when pruning top-level directories has been fixed.
1219 File::Find now also supports several other options to control its
1220 behavior. It can follow symbolic links if the C<follow> option is
1221 specified. Enabling the C<no_chdir> option will make File::Find skip
1222 changing the current directory when walking directories. The C<untaint>
1223 flag can be useful when running with taint checks enabled.
1229 This extension implements BSD-style file globbing. By default,
1230 it will also be used for the internal implementation of the glob()
1231 operator. See L<File::Glob>.
1235 New methods have been added to the File::Spec module: devnull() returns
1236 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1237 the temp directory (normally /tmp on Unix). There are now also methods
1238 to convert between absolute and relative filenames: abs2rel() and
1239 rel2abs(). For compatibility with operating systems that specify volume
1240 names in file paths, the splitpath(), splitdir(), and catdir() methods
1243 =item File::Spec::Functions
1245 The new File::Spec::Functions modules provides a function interface
1246 to the File::Spec module. Allows shorthand
1248 $fullname = catfile($dir1, $dir2, $file);
1252 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1256 Getopt::Long licensing has changed to allow the Perl Artistic License
1257 as well as the GPL. It used to be GPL only, which got in the way of
1258 non-GPL applications that wanted to use Getopt::Long.
1260 Getopt::Long encourages the use of Pod::Usage to produce help
1261 messages. For example:
1267 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1268 pod2usage(1) if $help;
1269 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1275 sample - Using GetOpt::Long and Pod::Usage
1279 sample [options] [file ...]
1282 -help brief help message
1283 -man full documentation
1291 Print a brief help message and exits.
1295 Prints the manual page and exits.
1301 B<This program> will read the given input file(s) and do someting
1302 useful with the contents thereof.
1306 See L<Pod::Usage> for details.
1308 A bug that prevented the non-option call-back E<lt>E<gt> from being
1309 specified as the first argument has been fixed.
1311 To specify the characters E<lt> and E<gt> as option starters, use
1312 E<gt>E<lt>. Note, however, that changing option starters is strongly
1317 write() and syswrite() will now accept a single-argument
1318 form of the call, for consistency with Perl's syswrite().
1320 You can now create a TCP-based IO::Socket::INET without forcing
1321 a connect attempt. This allows you to configure its options
1322 (like making it non-blocking) and then call connect() manually.
1324 A bug that prevented the IO::Socket::protocol() accessor
1325 from ever returning the correct value has been corrected.
1329 Java Perl Lingo is now distributed with Perl. See jpl/README
1330 for more information.
1334 C<use lib> now weeds out any trailing duplicate entries.
1335 C<no lib> removes all named entries.
1339 The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
1340 and C<~> are now supported on bigints.
1344 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1345 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1349 A little bit of radial trigonometry (cylindrical and spherical),
1350 radial coordinate conversions, and the great circle distance were added.
1354 [TODO - Brad Appleton <bradapp@enteract.com>]
1356 =item Pod::Text and Pod::Man
1358 [TODO - Russ Allbery <rra@stanford.edu>]
1362 An EXISTS method has been added to this module (and sdbm_exists() has
1363 been added to the underlying sdbm library), so one can now call exists
1364 on an SDBM_File tied hash and get the correct result, rather than a
1367 A bug that may have caused data loss when more than one disk block
1368 happens to be read from the database in a single FETCH() has been
1373 The timelocal() and timegm() functions used to silently return bogus
1374 results when the date fell outside the machine's integer range. They
1375 now consistently croak() if the date falls in an unsupported range.
1379 The error return value in list context has been changed for all functions
1380 that return a list of values. Previously these functions returned a list
1381 with a single element C<undef> if an error occurred. Now these functions
1382 return the empty list in these situations. This applies to the following
1388 The remaining functions are unchanged and continue to return C<undef> on
1389 error even in list context.
1391 The Win32::SetLastError(ERROR) function has been added as a complement
1392 to the Win32::GetLastError() function.
1394 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1395 pathname for FILENAME in scalar context. In list context it returns
1396 a two-element list containing the fully qualified directory name and
1397 the filename. See L<Win32>.
1401 A new feature called "DBM Filters" has been added to all the
1402 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1403 DBM Filters add four new methods to each DBM module:
1410 These can be used to filter key-value pairs before the pairs are
1411 written to the database or just after they are read from the database.
1412 See L<perldbmfilter> for further information.
1418 C<use attrs> is now obsolete, and is only provided for
1419 backward-compatibility. It's been replaced by the C<sub : attributes>
1420 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1422 C<use utf8> to enable UTF-8 and Unicode support.
1424 C<use caller 'encoding'> allows modules to inherit pragmatic attributes
1425 from the caller's context. C<encoding> is currently the only supported
1428 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1431 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1432 ...). Currently only one subpragma implemented, "use filetest
1433 'access';", that uses access(2) or equivalent to check permissions
1434 instead of using stat(2) as usual. This matters in filesystems
1435 where there are ACLs (access control lists): the stat(2) might lie,
1436 but access(2) knows better.
1438 =head1 Utility Changes
1442 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1446 C<perlcc> now supports the C and Bytecode backends. By default,
1447 it generates output from the simple C backend rather than the
1448 optimized C backend.
1450 Support for non-Unix platforms has been improved.
1455 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1457 =head1 Documentation Changes
1461 =item perlcompile.pod
1463 An introduction to using the Perl Compiler suite.
1465 =item perlfilter.pod
1467 An introduction to writing Perl source filters.
1471 Some guidelines for hacking the Perl source code.
1473 =item perlopentut.pod
1475 A tutorial on using open() effectively.
1477 =item perlreftut.pod
1479 A tutorial that introduces the essentials of references.
1483 A tutorial on managing class data for object modules.
1487 =head1 New or Changed Diagnostics
1491 =item "my sub" not yet implemented
1493 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1496 =item '!' allowed only after types %s
1498 (F) The '!' is allowed in pack() and unpack() only after certain types.
1499 See L<perlfunc/pack>.
1501 =item / cannot take a count
1503 (F) You had an unpack template indicating a counted-length string,
1504 but you have also specified an explicit size for the string.
1505 See L<perlfunc/pack>.
1507 =item / must be followed by a, A or Z
1509 (F) You had an unpack template indicating a counted-length string,
1510 which must be followed by one of the letters a, A or Z
1511 to indicate what sort of string is to be unpacked.
1512 See L<perlfunc/pack>.
1514 =item / must be followed by a*, A* or Z*
1516 (F) You had a pack template indicating a counted-length string,
1517 Currently the only things that can have their length counted are a*, A* or Z*.
1518 See L<perlfunc/pack>.
1520 =item / must follow a numeric type
1522 (F) You had an unpack template that contained a '#',
1523 but this did not follow some numeric unpack specification.
1524 See L<perlfunc/pack>.
1526 =item /%s/: Unrecognized escape \\%c passed through
1528 (W) You used a backslash-character combination which is not recognized
1529 by Perl. This combination appears in an interpolated variable or a
1530 C<'>-delimited regular expression. The character was understood literally.
1532 =item /%s/: Unrecognized escape \\%c in character class passed through
1534 (W) You used a backslash-character combination which is not recognized
1535 by Perl inside character classes. The character was understood literally.
1537 =item /%s/ should probably be written as "%s"
1539 (W) You have used a pattern where Perl expected to find a string,
1540 as in the first argument to C<join>. Perl will treat the true
1541 or false result of matching the pattern against $_ as the string,
1542 which is probably not what you had in mind.
1544 =item %s() called too early to check prototype
1546 (W) You've called a function that has a prototype before the parser saw a
1547 definition or declaration for it, and Perl could not check that the call
1548 conforms to the prototype. You need to either add an early prototype
1549 declaration for the subroutine in question, or move the subroutine
1550 definition ahead of the call to get proper prototype checking. Alternatively,
1551 if you are certain that you're calling the function correctly, you may put
1552 an ampersand before the name to avoid the warning. See L<perlsub>.
1554 =item %s package attribute may clash with future reserved word: %s
1556 (W) A lowercase attribute name was used that had a package-specific handler.
1557 That name might have a meaning to Perl itself some day, even though it
1558 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1561 =item (in cleanup) %s
1563 (W) This prefix usually indicates that a DESTROY() method raised
1564 the indicated exception. Since destructors are usually called by
1565 the system at arbitrary points during execution, and often a vast
1566 number of times, the warning is issued only once for any number
1567 of failures that would otherwise result in the same message being
1570 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1571 could also result in this warning. See L<perlcall/G_KEEPERR>.
1573 =item <> should be quotes
1575 (F) You wrote C<require E<lt>fileE<gt>> when you should have written
1578 =item Attempt to join self
1580 (F) You tried to join a thread from within itself, which is an
1581 impossible task. You may be joining the wrong thread, or you may
1582 need to move the join() to some other thread.
1584 =item Bad evalled substitution pattern
1586 (F) You've used the /e switch to evaluate the replacement for a
1587 substitution, but perl found a syntax error in the code to evaluate,
1588 most likely an unexpected right brace '}'.
1590 =item Bad realloc() ignored
1592 (S) An internal routine called realloc() on something that had never been
1593 malloc()ed in the first place. Mandatory, but can be disabled by
1594 setting environment variable C<PERL_BADFREE> to 1.
1596 =item Binary number > 0b11111111111111111111111111111111 non-portable
1598 (W) The binary number you specified is larger than 2**32-1
1599 (4294967295) and therefore non-portable between systems. See
1600 L<perlport> for more on portability concerns.
1602 =item Bit vector size > 32 non-portable
1604 (W) Using bit vector sizes larger than 32 is non-portable.
1606 =item Buffer overflow in prime_env_iter: %s
1608 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
1609 %ENV, it encountered a logical name or symbol definition which was too long,
1610 so it was truncated to the string shown.
1612 =item Can't check filesystem of script "%s"
1614 (P) For some reason you can't check the filesystem of the script for nosuid.
1616 =item Can't ignore signal CHLD, forcing to default
1618 (W) Perl has detected that it is being run with the SIGCHLD signal
1619 (sometimes known as SIGCLD) disabled. Since disabling this signal
1620 will interfere with proper determination of exit status of child
1621 processes, Perl has reset the signal to its default value.
1622 This situation typically indicates that the parent program under
1623 which Perl may be running (e.g. cron) is being very careless.
1625 =item Can't modify non-lvalue subroutine call
1627 (F) Subroutines meant to be used in lvalue context should be declared as
1628 such, see L<perlsub/"Lvalue subroutines">.
1630 =item Can't read CRTL environ
1632 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
1633 from the CRTL's internal environment array and discovered the array was
1634 missing. You need to figure out where your CRTL misplaced its environ
1635 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
1637 =item Can't remove %s: %s, skipping file
1639 (S) You requested an inplace edit without creating a backup file. Perl
1640 was unable to remove the original file to replace it with the modified
1641 file. The file was left unmodified.
1643 =item Can't return %s from lvalue subroutine
1645 (F) Perl detected an attempt to return illegal lvalues (such
1646 as temporary or readonly values) from a subroutine used as an lvalue.
1647 This is not allowed.
1649 =item Can't weaken a nonreference
1651 (F) You attempted to weaken something that was not a reference. Only
1652 references can be weakened.
1654 =item Character class [:%s:] unknown
1656 (F) The class in the character class [: :] syntax is unknown.
1659 =item Character class syntax [%s] belongs inside character classes
1661 (W) The character class constructs [: :], [= =], and [. .] go
1662 I<inside> character classes, the [] are part of the construct,
1663 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
1664 are not currently implemented; they are simply placeholders for
1667 =item Constant is not %s reference
1669 (F) A constant value (perhaps declared using the C<use constant> pragma)
1670 is being dereferenced, but it amounts to the wrong type of reference. The
1671 message indicates the type of reference that was expected. This usually
1672 indicates a syntax error in dereferencing the constant value.
1673 See L<perlsub/"Constant Functions"> and L<constant>.
1675 =item constant(%s): %%^H is not localized
1677 (F) When setting compile-time-lexicalized hash %^H one should set the
1678 corresponding bit of $^H as well.
1680 =item constant(%s): %s
1682 (F) Compile-time-substitutions (such as overloaded constants and
1683 character names) were not correctly set up.
1685 =item defined(@array) is deprecated
1687 (D) defined() is not usually useful on arrays because it checks for an
1688 undefined I<scalar> value. If you want to see if the array is empty,
1689 just use C<if (@array) { # not empty }> for example.
1691 =item defined(%hash) is deprecated
1693 (D) defined() is not usually useful on hashes because it checks for an
1694 undefined I<scalar> value. If you want to see if the hash is empty,
1695 just use C<if (%hash) { # not empty }> for example.
1697 =item Did not produce a valid header
1701 =item Document contains no data
1705 =item entering effective %s failed
1707 (F) While under the C<use filetest> pragma, switching the real and
1708 effective uids or gids failed.
1710 =item false [] range "%s" in regexp
1712 (W) A character class range must start and end at a literal character, not
1713 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
1714 range is interpreted as a literal "-". Consider quoting the "-", "\-".
1717 =item Filehandle %s opened only for output
1719 (W) You tried to read from a filehandle opened only for writing. If you
1720 intended it to be a read/write filehandle, you needed to open it with
1721 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
1722 you intended only to read from the file, use "E<lt>". See
1725 =item Hexadecimal number > 0xffffffff non-portable
1727 (W) The hexadecimal number you specified is larger than 2**32-1
1728 (4294967295) and therefore non-portable between systems. See
1729 L<perlport> for more on portability concerns.
1731 =item Ill-formed CRTL environ value "%s"
1733 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
1734 environ array, and encountered an element without the C<=> delimiter
1735 used to spearate keys from values. The element is ignored.
1737 =item Ill-formed message in prime_env_iter: |%s|
1739 (W) A warning peculiar to VMS. Perl tried to read a logical name
1740 or CLI symbol definition when preparing to iterate over %ENV, and
1741 didn't see the expected delimiter between key and value, so the
1744 =item Illegal binary digit %s
1746 (F) You used a digit other than 0 or 1 in a binary number.
1748 =item Illegal binary digit %s ignored
1750 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
1751 Interpretation of the binary number stopped before the offending digit.
1753 =item Illegal number of bits in vec
1755 (F) The number of bits in vec() (the third argument) must be a power of
1756 two from 1 to 32 (or 64, if your platform supports that).
1758 =item Integer overflow in %s number
1760 (W) The hexadecimal, octal or binary number you have specified either
1761 as a literal or as an argument to hex() or oct() is too big for your
1762 architecture, and has been converted to a floating point number. On a
1763 32-bit architecture the largest hexadecimal, octal or binary number
1764 representable without overflow is 0xFFFFFFFF, 037777777777, or
1765 0b11111111111111111111111111111111 respectively. Note that Perl
1766 transparently promotes all numbers to a floating point representation
1767 internally--subject to loss of precision errors in subsequent
1770 =item Invalid %s attribute: %s
1772 The indicated attribute for a subroutine or variable was not recognized
1773 by Perl or by a user-supplied handler. See L<attributes>.
1775 =item Invalid %s attributes: %s
1777 The indicated attributes for a subroutine or variable were not recognized
1778 by Perl or by a user-supplied handler. See L<attributes>.
1780 =item invalid [] range "%s" in regexp
1782 The offending range is now explicitly displayed.
1784 =item Invalid separator character %s in attribute list
1786 (F) Something other than a comma or whitespace was seen between the
1787 elements of an attribute list. If the previous attribute
1788 had a parenthesised parameter list, perhaps that list was terminated
1789 too soon. See L<attributes>.
1791 =item Invalid separator character %s in subroutine attribute list
1793 (F) Something other than a comma or whitespace was seen between the
1794 elements of a subroutine attribute list. If the previous attribute
1795 had a parenthesised parameter list, perhaps that list was terminated
1798 =item leaving effective %s failed
1800 (F) While under the C<use filetest> pragma, switching the real and
1801 effective uids or gids failed.
1803 =item Lvalue subs returning %s not implemented yet
1805 (F) Due to limitations in the current implementation, array and hash
1806 values cannot be returned in subroutines used in lvalue context.
1807 See L<perlsub/"Lvalue subroutines">.
1809 =item Method %s not permitted
1813 =item Missing %sbrace%s on \N{}
1815 (F) Wrong syntax of character name literal C<\N{charname}> within
1816 double-quotish context.
1818 =item Missing command in piped open
1820 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
1821 construction, but the command was missing or blank.
1823 =item Missing name in "my sub"
1825 (F) The reserved syntax for lexically scoped subroutines requires that they
1826 have a name with which they can be found.
1828 =item no UTC offset information; assuming local time is UTC
1830 (S) A warning peculiar to VMS. Perl was unable to find the local
1831 timezone offset, so it's assuming that local system time is equivalent
1832 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
1833 to translate to the number of seconds which need to be added to UTC to
1836 =item Octal number > 037777777777 non-portable
1838 (W) The octal number you specified is larger than 2**32-1 (4294967295)
1839 and therefore non-portable between systems. See L<perlport> for more
1840 on portability concerns.
1842 See also L<perlport> for writing portable code.
1844 =item panic: del_backref
1846 (P) Failed an internal consistency check while trying to reset a weak
1849 =item panic: kid popen errno read
1851 (F) forked child returned an incomprehensible message about its errno.
1853 =item panic: magic_killbackrefs
1855 (P) Failed an internal consistency check while trying to reset all weak
1856 references to an object.
1858 =item Possible Y2K bug: %s
1860 (W) You are concatenating the number 19 with another number, which
1861 could be a potential Year 2000 problem.
1863 =item Premature end of script headers
1867 =item Repeat count in pack overflows
1869 (F) You can't specify a repeat count so large that it overflows
1870 your signed integers. See L<perlfunc/pack>.
1872 =item Repeat count in unpack overflows
1874 (F) You can't specify a repeat count so large that it overflows
1875 your signed integers. See L<perlfunc/unpack>.
1877 =item realloc() of freed memory ignored
1879 (S) An internal routine called realloc() on something that had already
1882 =item Reference is already weak
1884 (W) You have attempted to weaken a reference that is already weak.
1885 Doing so has no effect.
1887 =item setpgrp can't take arguments
1889 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
1890 unlike POSIX setpgid(), which takes a process ID and process group ID.
1892 =item Strange *+?{} on zero-length expression
1894 (W) You applied a regular expression quantifier in a place where it
1895 makes no sense, such as on a zero-width assertion.
1896 Try putting the quantifier inside the assertion instead. For example,
1897 the way to match "abc" provided that it is followed by three
1898 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
1900 =item switching effective %s is not implemented
1902 (F) While under the C<use filetest> pragma, we cannot switch the
1903 real and effective uids or gids.
1905 =item This Perl can't reset CRTL environ elements (%s)
1907 =item This Perl can't set CRTL environ elements (%s=%s)
1909 (W) Warnings peculiar to VMS. You tried to change or delete an element
1910 of the CRTL's internal environ array, but your copy of Perl wasn't
1911 built with a CRTL that contained the setenv() function. You'll need to
1912 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
1913 L<perlvms>) so that the environ array isn't the target of the change to
1914 %ENV which produced the warning.
1916 =item Unknown open() mode '%s'
1918 (F) The second argument of 3-argument open() is not among the list
1919 of valid modes: C<L<lt>>, C<L<gt>>, C<E<gt>E<gt>>, C<+L<lt>>,
1920 C<+L<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|->.
1922 =item Unknown process %x sent message to prime_env_iter: %s
1924 (P) An error peculiar to VMS. Perl was reading values for %ENV before
1925 iterating over it, and someone else stuck a message in the stream of
1926 data Perl expected. Someone's very confused, or perhaps trying to
1927 subvert Perl's population of %ENV for nefarious purposes.
1929 =item Unrecognized escape \\%c passed through
1931 (W) You used a backslash-character combination which is not recognized
1932 by Perl. The character was understood literally.
1934 =item Unterminated attribute parameter in attribute list
1936 (F) The lexer saw an opening (left) parenthesis character while parsing an
1937 attribute list, but the matching closing (right) parenthesis
1938 character was not found. You may need to add (or remove) a backslash
1939 character to get your parentheses to balance. See L<attributes>.
1941 =item Unterminated attribute list
1943 (F) The lexer found something other than a simple identifier at the start
1944 of an attribute, and it wasn't a semicolon or the start of a
1945 block. Perhaps you terminated the parameter list of the previous attribute
1946 too soon. See L<attributes>.
1948 =item Unterminated attribute parameter in subroutine attribute list
1950 (F) The lexer saw an opening (left) parenthesis character while parsing a
1951 subroutine attribute list, but the matching closing (right) parenthesis
1952 character was not found. You may need to add (or remove) a backslash
1953 character to get your parentheses to balance.
1955 =item Unterminated subroutine attribute list
1957 (F) The lexer found something other than a simple identifier at the start
1958 of a subroutine attribute, and it wasn't a semicolon or the start of a
1959 block. Perhaps you terminated the parameter list of the previous attribute
1962 =item Value of CLI symbol "%s" too long
1964 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
1965 element from a CLI symbol table, and found a resultant string longer
1966 than 1024 characters. The return value has been truncated to 1024
1969 =item Version number must be a constant number
1971 (P) The attempt to translate a C<use Module n.n LIST> statement into
1972 its equivalent C<BEGIN> block found an internal inconsistency with
1977 =head1 Obsolete Diagnostics
1981 =item Character class syntax [: :] is reserved for future extensions
1983 (W) Within regular expression character classes ([]) the syntax beginning
1984 with "[:" and ending with ":]" is reserved for future extensions.
1985 If you need to represent those character sequences inside a regular
1986 expression character class, just quote the square brackets with the
1987 backslash: "\[:" and ":\]".
1989 =item Ill-formed logical name |%s| in prime_env_iter
1991 (W) A warning peculiar to VMS. A logical name was encountered when preparing
1992 to iterate over %ENV which violates the syntactic rules governing logical
1993 names. Because it cannot be translated normally, it is skipped, and will not
1994 appear in %ENV. This may be a benign occurrence, as some software packages
1995 might directly modify logical name tables and introduce nonstandard names,
1996 or it may indicate that a logical name table has been corrupted.
1998 =item regexp too big
2000 (F) The current implementation of regular expressions uses shorts as
2001 address offsets within a string. Unfortunately this means that if
2002 the regular expression compiles to longer than 32767, it'll blow up.
2003 Usually when you want a regular expression this big, there is a better
2004 way to do it with multiple statements. See L<perlre>.
2006 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2008 (D) Perl versions before 5.004 misinterpreted any type marker followed
2009 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2010 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2012 However, the developers of Perl 5.004 could not fix this bug completely,
2013 because at least two widely-used modules depend on the old meaning of
2014 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2015 old (broken) way inside strings; but it generates this message as a
2016 warning. And in Perl 5.005, this special treatment will cease.
2022 If you find what you think is a bug, you might check the
2023 articles recently posted to the comp.lang.perl.misc newsgroup.
2024 There may also be information at http://www.perl.com/perl/, the Perl
2027 If you believe you have an unreported bug, please run the B<perlbug>
2028 program included with your release. Make sure to trim your bug down
2029 to a tiny but sufficient test case. Your bug report, along with the
2030 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2031 analysed by the Perl porting team.
2035 The F<Changes> file for exhaustive details on what changed.
2037 The F<INSTALL> file for how to build Perl.
2039 The F<README> file for general stuff.
2041 The F<Artistic> and F<Copying> files for copyright information.
2045 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2046 contributions from The Perl Porters.
2048 Send omissions or corrections to <F<perlbug@perl.com>>.