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1=head1 NAME
2
1eb1bad9 3perl561delta - what's new for perl v5.6.1
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4
5=head1 DESCRIPTION
6
7This document describes differences between the 5.005 release and the 5.6.1
8release.
9
10=head1 Summary of changes between 5.6.0 and 5.6.1
11
12This section contains a summary of the changes between the 5.6.0 release
13and the 5.6.1 release. More details about the changes mentioned here
14may be found in the F<Changes> files that accompany the Perl source
15distribution. See L<perlhack> for pointers to online resources where you
16can inspect the individual patches described by these changes.
17
18=head2 Security Issues
19
20suidperl will not run /bin/mail anymore, because some platforms have
21a /bin/mail that is vulnerable to buffer overflow attacks.
22
23Note that suidperl is neither built nor installed by default in
24any recent version of perl. Use of suidperl is highly discouraged.
25If you think you need it, try alternatives such as sudo first.
1577cd80 26See http://www.courtesan.com/sudo/ .
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27
28=head2 Core bug fixes
29
30This is not an exhaustive list. It is intended to cover only the
31significant user-visible changes.
32
33=over
34
35=item C<UNIVERSAL::isa()>
36
37A bug in the caching mechanism used by C<UNIVERSAL::isa()> that affected
38base.pm has been fixed. The bug has existed since the 5.005 releases,
39but wasn't tickled by base.pm in those releases.
40
41=item Memory leaks
42
43Various cases of memory leaks and attempts to access uninitialized memory
44have been cured. See L</"Known Problems"> below for further issues.
45
46=item Numeric conversions
47
48Numeric conversions did not recognize changes in the string value
49properly in certain circumstances.
50
51In other situations, large unsigned numbers (those above 2**31) could
52sometimes lose their unsignedness, causing bogus results in arithmetic
53operations.
54
55Integer modulus on large unsigned integers sometimes returned
56incorrect values.
57
58Perl 5.6.0 generated "not a number" warnings on certain conversions where
59previous versions didn't.
60
61These problems have all been rectified.
62
63Infinity is now recognized as a number.
64
65=item qw(a\\b)
66
67In Perl 5.6.0, qw(a\\b) produced a string with two backslashes instead
68of one, in a departure from the behavior in previous versions. The
69older behavior has been reinstated.
70
71=item caller()
72
73caller() could cause core dumps in certain situations. Carp was sometimes
74affected by this problem.
75
76=item Bugs in regular expressions
77
78Pattern matches on overloaded values are now handled correctly.
79
80Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading to spurious warnings.
81This has been corrected.
82
83The RE engine found in Perl 5.6.0 accidentally pessimised certain kinds
84of simple pattern matches. These are now handled better.
85
86Regular expression debug output (whether through C<use re 'debug'>
87or via C<-Dr>) now looks better.
88
89Multi-line matches like C<"a\nxb\n" =~ /(?!\A)x/m> were flawed. The
90bug has been fixed.
91
92Use of $& could trigger a core dump under some situations. This
93is now avoided.
94
95Match variables $1 et al., weren't being unset when a pattern match
96was backtracking, and the anomaly showed up inside C</...(?{ ... }).../>
97etc. These variables are now tracked correctly.
98
99pos() did not return the correct value within s///ge in earlier
100versions. This is now handled correctly.
101
102=item "slurp" mode
103
104readline() on files opened in "slurp" mode could return an extra "" at
105the end in certain situations. This has been corrected.
106
107=item Autovivification of symbolic references to special variables
108
109Autovivification of symbolic references of special variables described
110in L<perlvar> (as in C<${$num}>) was accidentally disabled. This works
111again now.
112
113=item Lexical warnings
114
115Lexical warnings now propagate correctly into C<eval "...">.
116
117C<use warnings qw(FATAL all)> did not work as intended. This has been
118corrected.
119
120Lexical warnings could leak into other scopes in some situations.
121This is now fixed.
122
123warnings::enabled() now reports the state of $^W correctly if the caller
124isn't using lexical warnings.
125
126=item Spurious warnings and errors
127
128Perl 5.6.0 could emit spurious warnings about redefinition of dl_error()
129when statically building extensions into perl. This has been corrected.
130
131"our" variables could result in bogus "Variable will not stay shared"
132warnings. This is now fixed.
133
134"our" variables of the same name declared in two sibling blocks
135resulted in bogus warnings about "redeclaration" of the variables.
136The problem has been corrected.
137
138=item glob()
139
140Compatibility of the builtin glob() with old csh-based glob has been
141improved with the addition of GLOB_ALPHASORT option. See C<File::Glob>.
142
143File::Glob::glob() has been renamed to File::Glob::bsd_glob()
144because the name clashes with the builtin glob(). The older
145name is still available for compatibility, but is deprecated.
146
147Spurious syntax errors generated in certain situations, when glob()
148caused File::Glob to be loaded for the first time, have been fixed.
149
150=item Tainting
151
152Some cases of inconsistent taint propagation (such as within hash
153values) have been fixed.
154
155The tainting behavior of sprintf() has been rationalized. It does
156not taint the result of floating point formats anymore, making the
157behavior consistent with that of string interpolation.
158
159=item sort()
160
161Arguments to sort() weren't being provided the right wantarray() context.
162The comparison block is now run in scalar context, and the arguments to
163be sorted are always provided list context.
164
165sort() is also fully reentrant, in the sense that the sort function
166can itself call sort(). This did not work reliably in previous releases.
167
168=item #line directives
169
170#line directives now work correctly when they appear at the very
171beginning of C<eval "...">.
172
173=item Subroutine prototypes
174
175The (\&) prototype now works properly.
176
177=item map()
178
179map() could get pathologically slow when the result list it generates
180is larger than the source list. The performance has been improved for
181common scenarios.
182
183=item Debugger
184
185Debugger exit code now reflects the script exit code.
186
187Condition C<"0"> in breakpoints is now treated correctly.
188
189The C<d> command now checks the line number.
190
191C<$.> is no longer corrupted by the debugger.
192
193All debugger output now correctly goes to the socket if RemotePort
194is set.
195
196=item PERL5OPT
197
198PERL5OPT can be set to more than one switch group. Previously,
199it used to be limited to one group of options only.
200
201=item chop()
202
203chop(@list) in list context returned the characters chopped in reverse
204order. This has been reversed to be in the right order.
205
206=item Unicode support
207
208Unicode support has seen a large number of incremental improvements,
209but continues to be highly experimental. It is not expected to be
210fully supported in the 5.6.x maintenance releases.
211
212substr(), join(), repeat(), reverse(), quotemeta() and string
213concatenation were all handling Unicode strings incorrectly in
214Perl 5.6.0. This has been corrected.
215
216Support for C<tr///CU> and C<tr///UC> etc., have been removed since
217we realized the interface is broken. For similar functionality,
218see L<perlfunc/pack>.
219
220The Unicode Character Database has been updated to version 3.0.1
221with additions made available to the public as of August 30, 2000.
222
223The Unicode character classes \p{Blank} and \p{SpacePerl} have been
224added. "Blank" is like C isblank(), that is, it contains only
225"horizontal whitespace" (the space character is, the newline isn't),
226and the "SpacePerl" is the Unicode equivalent of C<\s> (\p{Space}
227isn't, since that includes the vertical tabulator character, whereas
228C<\s> doesn't.)
229
230If you are experimenting with Unicode support in perl, the development
231versions of Perl may have more to offer. In particular, I/O layers
232are now available in the development track, but not in the maintenance
233track, primarily to do backward compatibility issues. Unicode support
234is also evolving rapidly on a daily basis in the development track--the
235maintenance track only reflects the most conservative of these changes.
236
237=item 64-bit support
238
239Support for 64-bit platforms has been improved, but continues to be
240experimental. The level of support varies greatly among platforms.
241
242=item Compiler
243
244The B Compiler and its various backends have had many incremental
245improvements, but they continue to remain highly experimental. Use in
246production environments is discouraged.
247
248The perlcc tool has been rewritten so that the user interface is much
249more like that of a C compiler.
250
251The perlbc tools has been removed. Use C<perlcc -B> instead.
252
253=item Lvalue subroutines
254
255There have been various bugfixes to support lvalue subroutines better.
256However, the feature still remains experimental.
257
258=item IO::Socket
259
260IO::Socket::INET failed to open the specified port if the service
261name was not known. It now correctly uses the supplied port number
262as is.
263
264=item File::Find
265
266File::Find now chdir()s correctly when chasing symbolic links.
267
268=item xsubpp
269
270xsubpp now tolerates embedded POD sections.
271
272=item C<no Module;>
273
274C<no Module;> does not produce an error even if Module does not have an
275unimport() method. This parallels the behavior of C<use> vis-a-vis
276C<import>.
277
278=item Tests
279
280A large number of tests have been added.
281
282=back
283
284=head2 Core features
285
286untie() will now call an UNTIE() hook if it exists. See L<perltie>
287for details.
288
289The C<-DT> command line switch outputs copious tokenizing information.
290See L<perlrun>.
291
292Arrays are now always interpolated in double-quotish strings. Previously,
293C<"foo@bar.com"> used to be a fatal error at compile time, if an array
294C<@bar> was not used or declared. This transitional behavior was
295intended to help migrate perl4 code, and is deemed to be no longer useful.
296See L</"Arrays now always interpolate into double-quoted strings">.
297
298keys(), each(), pop(), push(), shift(), splice() and unshift()
299can all be overridden now.
300
301C<my __PACKAGE__ $obj> now does the expected thing.
302
303=head2 Configuration issues
304
305On some systems (IRIX and Solaris among them) the system malloc is demonstrably
306better. While the defaults haven't been changed in order to retain binary
307compatibility with earlier releases, you may be better off building perl
308with C<Configure -Uusemymalloc ...> as discussed in the F<INSTALL> file.
309
310C<Configure> has been enhanced in various ways:
311
312=over
313
314=item *
315
316Minimizes use of temporary files.
317
318=item *
319
320By default, does not link perl with libraries not used by it, such as
321the various dbm libraries. SunOS 4.x hints preserve behavior on that
322platform.
323
324=item *
325
326Support for pdp11-style memory models has been removed due to obsolescence.
327
328=item *
329
330Building outside the source tree is supported on systems that have
331symbolic links. This is done by running
332
333 sh /path/to/source/Configure -Dmksymlinks ...
334 make all test install
335
336in a directory other than the perl source directory. See F<INSTALL>.
337
338=item *
339
340C<Configure -S> can be run non-interactively.
341
342=back
343
344=head2 Documentation
345
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346README.aix, README.solaris and README.macos have been added.
347README.posix-bc has been renamed to README.bs2000. These are
348installed as L<perlaix>, L<perlsolaris>, L<perlmacos>, and
349L<perlbs2000> respectively.
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350
351The following pod documents are brand new:
352
353 perlclib Internal replacements for standard C library functions
354 perldebtut Perl debugging tutorial
355 perlebcdic Considerations for running Perl on EBCDIC platforms
356 perlnewmod Perl modules: preparing a new module for distribution
357 perlrequick Perl regular expressions quick start
358 perlretut Perl regular expressions tutorial
359 perlutil utilities packaged with the Perl distribution
360
361The F<INSTALL> file has been expanded to cover various issues, such as
36264-bit support.
363
364A longer list of contributors has been added to the source distribution.
365See the file C<AUTHORS>.
366
367Numerous other changes have been made to the included documentation and FAQs.
368
369=head2 Bundled modules
370
371The following modules have been added.
372
373=over
374
375=item B::Concise
376
377Walks Perl syntax tree, printing concise info about ops. See L<B::Concise>.
378
379=item File::Temp
380
381Returns name and handle of a temporary file safely. See L<File::Temp>.
382
383=item Pod::LaTeX
384
385Converts Pod data to formatted LaTeX. See L<Pod::LaTeX>.
386
387=item Pod::Text::Overstrike
388
389Converts POD data to formatted overstrike text. See L<Pod::Text::Overstrike>.
390
391=back
392
393The following modules have been upgraded.
394
395=over
396
397=item CGI
398
399CGI v2.752 is now included.
400
401=item CPAN
402
403CPAN v1.59_54 is now included.
404
405=item Class::Struct
406
407Various bugfixes have been added.
408
409=item DB_File
410
411DB_File v1.75 supports newer Berkeley DB versions, among other
412improvements.
413
414=item Devel::Peek
415
416Devel::Peek has been enhanced to support dumping of memory statistics,
417when perl is built with the included malloc().
418
419=item File::Find
420
421File::Find now supports pre and post-processing of the files in order
422to sort() them, etc.
423
424=item Getopt::Long
425
426Getopt::Long v2.25 is included.
427
428=item IO::Poll
429
430Various bug fixes have been included.
431
432=item IPC::Open3
433
434IPC::Open3 allows use of numeric file descriptors.
435
436=item Math::BigFloat
437
438The fmod() function supports modulus operations. Various bug fixes
439have also been included.
440
441=item Math::Complex
442
443Math::Complex handles inf, NaN etc., better.
444
445=item Net::Ping
446
447ping() could fail on odd number of data bytes, and when the echo service
448isn't running. This has been corrected.
449
450=item Opcode
451
452A memory leak has been fixed.
453
454=item Pod::Parser
455
456Version 1.13 of the Pod::Parser suite is included.
457
458=item Pod::Text
459
460Pod::Text and related modules have been upgraded to the versions
461in podlators suite v2.08.
462
463=item SDBM_File
464
465On dosish platforms, some keys went missing because of lack of support for
466files with "holes". A workaround for the problem has been added.
467
468=item Sys::Syslog
469
470Various bug fixes have been included.
471
472=item Tie::RefHash
473
474Now supports Tie::RefHash::Nestable to automagically tie hashref values.
475
476=item Tie::SubstrHash
477
478Various bug fixes have been included.
479
480=back
481
482=head2 Platform-specific improvements
483
484The following new ports are now available.
485
486=over
487
488=item NCR MP-RAS
489
490=item NonStop-UX
491
492=back
493
494Perl now builds under Amdahl UTS.
495
496Perl has also been verified to build under Amiga OS.
497
498Support for EPOC has been much improved. See README.epoc.
499
500Building perl with -Duseithreads or -Duse5005threads now works
501under HP-UX 10.20 (previously it only worked under 10.30 or later).
502You will need a thread library package installed. See README.hpux.
503
504Long doubles should now work under Linux.
505
8939ba94 506Mac OS Classic is now supported in the mainstream source package.
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507See README.macos.
508
509Support for MPE/iX has been updated. See README.mpeix.
510
511Support for OS/2 has been improved. See C<os2/Changes> and README.os2.
512
513Dynamic loading on z/OS (formerly OS/390) has been improved. See
514README.os390.
515
516Support for VMS has seen many incremental improvements, including
517better support for operators like backticks and system(), and better
518%ENV handling. See C<README.vms> and L<perlvms>.
519
520Support for Stratus VOS has been improved. See C<vos/Changes> and README.vos.
521
522Support for Windows has been improved.
523
524=over
525
526=item *
527
528fork() emulation has been improved in various ways, but still continues
529to be experimental. See L<perlfork> for known bugs and caveats.
530
531=item *
532
533%SIG has been enabled under USE_ITHREADS, but its use is completely
534unsupported under all configurations.
535
536=item *
537
538Borland C++ v5.5 is now a supported compiler that can build Perl.
539However, the generated binaries continue to be incompatible with those
540generated by the other supported compilers (GCC and Visual C++).
541
542=item *
543
544Non-blocking waits for child processes (or pseudo-processes) are
545supported via C<waitpid($pid, &POSIX::WNOHANG)>.
546
547=item *
548
549A memory leak in accept() has been fixed.
550
551=item *
552
553wait(), waitpid() and backticks now return the correct exit status under
554Windows 9x.
555
556=item *
557
558Trailing new %ENV entries weren't propagated to child processes. This
559is now fixed.
560
561=item *
562
563Current directory entries in %ENV are now correctly propagated to child
564processes.
565
566=item *
567
568Duping socket handles with open(F, ">&MYSOCK") now works under Windows 9x.
569
570=item *
571
572The makefiles now provide a single switch to bulk-enable all the features
573enabled in ActiveState ActivePerl (a popular binary distribution).
574
575=item *
576
577Win32::GetCwd() correctly returns C:\ instead of C: when at the drive root.
578Other bugs in chdir() and Cwd::cwd() have also been fixed.
579
580=item *
581
582fork() correctly returns undef and sets EAGAIN when it runs out of
583pseudo-process handles.
584
585=item *
586
587ExtUtils::MakeMaker now uses $ENV{LIB} to search for libraries.
588
589=item *
590
591UNC path handling is better when perl is built to support fork().
592
593=item *
594
595A handle leak in socket handling has been fixed.
596
597=item *
598
599send() works from within a pseudo-process.
600
601=back
602
603Unless specifically qualified otherwise, the remainder of this document
604covers changes between the 5.005 and 5.6.0 releases.
7207e29d 605
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606=head1 Core Enhancements
607
608=head2 Interpreter cloning, threads, and concurrency
609
610Perl 5.6.0 introduces the beginnings of support for running multiple
611interpreters concurrently in different threads. In conjunction with
612the perl_clone() API call, which can be used to selectively duplicate
613the state of any given interpreter, it is possible to compile a
614piece of code once in an interpreter, clone that interpreter
615one or more times, and run all the resulting interpreters in distinct
616threads.
617
618On the Windows platform, this feature is used to emulate fork() at the
619interpreter level. See L<perlfork> for details about that.
620
621This feature is still in evolution. It is eventually meant to be used
622to selectively clone a subroutine and data reachable from that
623subroutine in a separate interpreter and run the cloned subroutine
624in a separate thread. Since there is no shared data between the
625interpreters, little or no locking will be needed (unless parts of
626the symbol table are explicitly shared). This is obviously intended
627to be an easy-to-use replacement for the existing threads support.
628
629Support for cloning interpreters and interpreter concurrency can be
630enabled using the -Dusethreads Configure option (see win32/Makefile for
631how to enable it on Windows.) The resulting perl executable will be
632functionally identical to one that was built with -Dmultiplicity, but
633the perl_clone() API call will only be available in the former.
634
635-Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn
636enables Perl source code changes that provide a clear separation between
637the op tree and the data it operates with. The former is immutable, and
638can therefore be shared between an interpreter and all of its clones,
639while the latter is considered local to each interpreter, and is therefore
640copied for each clone.
641
642Note that building Perl with the -Dusemultiplicity Configure option
643is adequate if you wish to run multiple B<independent> interpreters
644concurrently in different threads. -Dusethreads only provides the
645additional functionality of the perl_clone() API call and other
646support for running B<cloned> interpreters concurrently.
647
648 NOTE: This is an experimental feature. Implementation details are
649 subject to change.
650
651=head2 Lexically scoped warning categories
652
653You can now control the granularity of warnings emitted by perl at a finer
654level using the C<use warnings> pragma. L<warnings> and L<perllexwarn>
655have copious documentation on this feature.
656
657=head2 Unicode and UTF-8 support
658
659Perl now uses UTF-8 as its internal representation for character
660strings. The C<utf8> and C<bytes> pragmas are used to control this support
661in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
662more information.
663
664This feature is expected to evolve quickly to support some form of I/O
665disciplines that can be used to specify the kind of input and output data
666(bytes or characters). Until that happens, additional modules from CPAN
667will be needed to complete the toolkit for dealing with Unicode.
668
669 NOTE: This should be considered an experimental feature. Implementation
670 details are subject to change.
671
672=head2 Support for interpolating named characters
673
674The new C<\N> escape interpolates named characters within strings.
675For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string
676with a Unicode smiley face at the end.
677
678=head2 "our" declarations
679
680An "our" declaration introduces a value that can be best understood
681as a lexically scoped symbolic alias to a global variable in the
682package that was current where the variable was declared. This is
683mostly useful as an alternative to the C<vars> pragma, but also provides
684the opportunity to introduce typing and other attributes for such
685variables. See L<perlfunc/our>.
686
687=head2 Support for strings represented as a vector of ordinals
688
689Literals of the form C<v1.2.3.4> are now parsed as a string composed
690of characters with the specified ordinals. This is an alternative, more
691readable way to construct (possibly Unicode) strings instead of
692interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
693C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
694parsed the same as C<v1.2.3>.
695
696Strings written in this form are also useful to represent version "numbers".
697It is easy to compare such version "numbers" (which are really just plain
698strings) using any of the usual string comparison operators C<eq>, C<ne>,
699C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
700C<&>, etc.
701
702In conjunction with the new C<$^V> magic variable (which contains
703the perl version as a string), such literals can be used as a readable way
704to check if you're running a particular version of Perl:
705
706 # this will parse in older versions of Perl also
707 if ($^V and $^V gt v5.6.0) {
708 # new features supported
709 }
710
711C<require> and C<use> also have some special magic to support such literals.
712They will be interpreted as a version rather than as a module name:
713
714 require v5.6.0; # croak if $^V lt v5.6.0
715 use v5.6.0; # same, but croaks at compile-time
716
717Alternatively, the C<v> may be omitted if there is more than one dot:
718
719 require 5.6.0;
720 use 5.6.0;
721
722Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
723to print ordinals of characters in arbitrary strings:
724
725 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
726 printf "%*vX", ":", $addr; # formats IPv6 address
727 printf "%*vb", " ", $bits; # displays bitstring
728
729See L<perldata/"Scalar value constructors"> for additional information.
730
731=head2 Improved Perl version numbering system
732
733Beginning with Perl version 5.6.0, the version number convention has been
734changed to a "dotted integer" scheme that is more commonly found in open
735source projects.
736
737Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
738The next development series following v5.6.0 will be numbered v5.7.x,
739beginning with v5.7.0, and the next major production release following
740v5.6.0 will be v5.8.0.
741
742The English module now sets $PERL_VERSION to $^V (a string value) rather
743than C<$]> (a numeric value). (This is a potential incompatibility.
744Send us a report via perlbug if you are affected by this.)
745
746The v1.2.3 syntax is also now legal in Perl.
747See L<Support for strings represented as a vector of ordinals> for more on that.
748
749To cope with the new versioning system's use of at least three significant
750digits for each version component, the method used for incrementing the
751subversion number has also changed slightly. We assume that versions older
752than v5.6.0 have been incrementing the subversion component in multiples of
75310. Versions after v5.6.0 will increment them by 1. Thus, using the new
754notation, 5.005_03 is the "same" as v5.5.30, and the first maintenance
755version following v5.6.0 will be v5.6.1 (which should be read as being
756equivalent to a floating point value of 5.006_001 in the older format,
757stored in C<$]>).
758
759=head2 New syntax for declaring subroutine attributes
760
761Formerly, if you wanted to mark a subroutine as being a method call or
762as requiring an automatic lock() when it is entered, you had to declare
763that with a C<use attrs> pragma in the body of the subroutine.
764That can now be accomplished with declaration syntax, like this:
765
4358a253 766 sub mymethod : locked method;
493a87da
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767 ...
768 sub mymethod : locked method {
769 ...
770 }
771
4358a253 772 sub othermethod :locked :method;
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773 ...
774 sub othermethod :locked :method {
775 ...
776 }
777
778
779(Note how only the first C<:> is mandatory, and whitespace surrounding
780the C<:> is optional.)
781
782F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
783with the stubs they provide. See L<attributes>.
784
785=head2 File and directory handles can be autovivified
786
787Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
788handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
789socket(), and accept()) now autovivify a file or directory handle
790if the handle passed to them is an uninitialized scalar variable. This
791allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
792to be used to create filehandles that will conveniently be closed
793automatically when the scope ends, provided there are no other references
794to them. This largely eliminates the need for typeglobs when opening
795filehandles that must be passed around, as in the following example:
796
797 sub myopen {
798 open my $fh, "@_"
799 or die "Can't open '@_': $!";
800 return $fh;
801 }
802
803 {
804 my $f = myopen("</etc/motd");
805 print <$f>;
806 # $f implicitly closed here
807 }
808
809=head2 open() with more than two arguments
810
811If open() is passed three arguments instead of two, the second argument
812is used as the mode and the third argument is taken to be the file name.
813This is primarily useful for protecting against unintended magic behavior
814of the traditional two-argument form. See L<perlfunc/open>.
815
816=head2 64-bit support
817
818Any platform that has 64-bit integers either
819
820 (1) natively as longs or ints
821 (2) via special compiler flags
822 (3) using long long or int64_t
823
824is able to use "quads" (64-bit integers) as follows:
825
826=over 4
827
828=item *
829
830constants (decimal, hexadecimal, octal, binary) in the code
831
832=item *
833
834arguments to oct() and hex()
835
836=item *
837
838arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
839
840=item *
841
842printed as such
843
844=item *
845
846pack() and unpack() "q" and "Q" formats
847
848=item *
849
850in basic arithmetics: + - * / % (NOTE: operating close to the limits
851of the integer values may produce surprising results)
852
853=item *
854
855in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
856to be 32 bits wide but now operate on the full native width.)
857
858=item *
859
860vec()
861
862=back
863
864Note that unless you have the case (a) you will have to configure
865and compile Perl using the -Duse64bitint Configure flag.
866
867 NOTE: The Configure flags -Duselonglong and -Duse64bits have been
868 deprecated. Use -Duse64bitint instead.
869
870There are actually two modes of 64-bitness: the first one is achieved
871using Configure -Duse64bitint and the second one using Configure
872-Duse64bitall. The difference is that the first one is minimal and
873the second one maximal. The first works in more places than the second.
874
875The C<use64bitint> does only as much as is required to get 64-bit
876integers into Perl (this may mean, for example, using "long longs")
877while your memory may still be limited to 2 gigabytes (because your
878pointers could still be 32-bit). Note that the name C<64bitint> does
879not imply that your C compiler will be using 64-bit C<int>s (it might,
880but it doesn't have to): the C<use64bitint> means that you will be
881able to have 64 bits wide scalar values.
882
883The C<use64bitall> goes all the way by attempting to switch also
884integers (if it can), longs (and pointers) to being 64-bit. This may
885create an even more binary incompatible Perl than -Duse64bitint: the
886resulting executable may not run at all in a 32-bit box, or you may
887have to reboot/reconfigure/rebuild your operating system to be 64-bit
888aware.
889
890Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
891nor -Duse64bitall.
892
893Last but not least: note that due to Perl's habit of always using
894floating point numbers, the quads are still not true integers.
895When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
896-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
897are silently promoted to floating point numbers, after which they will
898start losing precision (in their lower digits).
899
900 NOTE: 64-bit support is still experimental on most platforms.
901 Existing support only covers the LP64 data model. In particular, the
902 LLP64 data model is not yet supported. 64-bit libraries and system
903 APIs on many platforms have not stabilized--your mileage may vary.
904
905=head2 Large file support
906
907If you have filesystems that support "large files" (files larger than
9082 gigabytes), you may now also be able to create and access them from
909Perl.
910
911 NOTE: The default action is to enable large file support, if
912 available on the platform.
913
914If the large file support is on, and you have a Fcntl constant
915O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
916of sysopen().
917
918Beware that unless your filesystem also supports "sparse files" seeking
919to umpteen petabytes may be inadvisable.
920
921Note that in addition to requiring a proper file system to do large
922files you may also need to adjust your per-process (or your
923per-system, or per-process-group, or per-user-group) maximum filesize
924limits before running Perl scripts that try to handle large files,
925especially if you intend to write such files.
926
927Finally, in addition to your process/process group maximum filesize
928limits, you may have quota limits on your filesystems that stop you
929(your user id or your user group id) from using large files.
930
931Adjusting your process/user/group/file system/operating system limits
932is outside the scope of Perl core language. For process limits, you
933may try increasing the limits using your shell's limits/limit/ulimit
934command before running Perl. The BSD::Resource extension (not
935included with the standard Perl distribution) may also be of use, it
936offers the getrlimit/setrlimit interface that can be used to adjust
937process resource usage limits, including the maximum filesize limit.
938
939=head2 Long doubles
940
941In some systems you may be able to use long doubles to enhance the
942range and precision of your double precision floating point numbers
943(that is, Perl's numbers). Use Configure -Duselongdouble to enable
944this support (if it is available).
945
946=head2 "more bits"
947
948You can "Configure -Dusemorebits" to turn on both the 64-bit support
949and the long double support.
950
951=head2 Enhanced support for sort() subroutines
952
953Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can
954now be used as sort subroutines. In either case, the two elements to
955be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
956
957For unprototyped sort subroutines, the historical behavior of passing
958the elements to be compared as the global variables $a and $b remains
959unchanged.
960
961=head2 C<sort $coderef @foo> allowed
962
963sort() did not accept a subroutine reference as the comparison
964function in earlier versions. This is now permitted.
965
966=head2 File globbing implemented internally
967
968Perl now uses the File::Glob implementation of the glob() operator
969automatically. This avoids using an external csh process and the
970problems associated with it.
971
972 NOTE: This is currently an experimental feature. Interfaces and
973 implementation are subject to change.
974
975=head2 Support for CHECK blocks
976
977In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
978subroutines named C<CHECK> are now special. These are queued up during
979compilation and behave similar to END blocks, except they are called at
980the end of compilation rather than at the end of execution. They cannot
981be called directly.
982
983=head2 POSIX character class syntax [: :] supported
984
985For example to match alphabetic characters use /[[:alpha:]]/.
986See L<perlre> for details.
987
988=head2 Better pseudo-random number generator
989
990In 5.005_0x and earlier, perl's rand() function used the C library
991rand(3) function. As of 5.005_52, Configure tests for drand48(),
992random(), and rand() (in that order) and picks the first one it finds.
993
994These changes should result in better random numbers from rand().
995
996=head2 Improved C<qw//> operator
997
998The C<qw//> operator is now evaluated at compile time into a true list
999instead of being replaced with a run time call to C<split()>. This
1000removes the confusing misbehaviour of C<qw//> in scalar context, which
1001had inherited that behaviour from split().
1002
1003Thus:
1004
1005 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
1006
1007now correctly prints "3|a", instead of "2|a".
1008
1009=head2 Better worst-case behavior of hashes
1010
1011Small changes in the hashing algorithm have been implemented in
1012order to improve the distribution of lower order bits in the
1013hashed value. This is expected to yield better performance on
1014keys that are repeated sequences.
1015
1016=head2 pack() format 'Z' supported
1017
1018The new format type 'Z' is useful for packing and unpacking null-terminated
1019strings. See L<perlfunc/"pack">.
1020
1021=head2 pack() format modifier '!' supported
1022
1023The new format type modifier '!' is useful for packing and unpacking
1024native shorts, ints, and longs. See L<perlfunc/"pack">.
1025
1026=head2 pack() and unpack() support counted strings
1027
1028The template character '/' can be used to specify a counted string
1029type to be packed or unpacked. See L<perlfunc/"pack">.
1030
1031=head2 Comments in pack() templates
1032
1033The '#' character in a template introduces a comment up to
1034end of the line. This facilitates documentation of pack()
1035templates.
1036
1037=head2 Weak references
1038
1039In previous versions of Perl, you couldn't cache objects so as
1040to allow them to be deleted if the last reference from outside
1041the cache is deleted. The reference in the cache would hold a
1042reference count on the object and the objects would never be
1043destroyed.
1044
1045Another familiar problem is with circular references. When an
1046object references itself, its reference count would never go
1047down to zero, and it would not get destroyed until the program
1048is about to exit.
1049
1050Weak references solve this by allowing you to "weaken" any
1051reference, that is, make it not count towards the reference count.
1052When the last non-weak reference to an object is deleted, the object
1053is destroyed and all the weak references to the object are
1054automatically undef-ed.
1055
1bb10054 1056To use this feature, you need the Devel::WeakRef package from CPAN, which
493a87da
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1057contains additional documentation.
1058
1059 NOTE: This is an experimental feature. Details are subject to change.
1060
1061=head2 Binary numbers supported
1062
1063Binary numbers are now supported as literals, in s?printf formats, and
1064C<oct()>:
1065
1066 $answer = 0b101010;
1067 printf "The answer is: %b\n", oct("0b101010");
1068
1069=head2 Lvalue subroutines
1070
1071Subroutines can now return modifiable lvalues.
1072See L<perlsub/"Lvalue subroutines">.
1073
1074 NOTE: This is an experimental feature. Details are subject to change.
1075
1076=head2 Some arrows may be omitted in calls through references
1077
1078Perl now allows the arrow to be omitted in many constructs
1079involving subroutine calls through references. For example,
1080C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
1081This is rather similar to how the arrow may be omitted from
1082C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
1083required for C<< foo(10)->('bar') >>.
1084
1085=head2 Boolean assignment operators are legal lvalues
1086
1087Constructs such as C<($a ||= 2) += 1> are now allowed.
1088
1089=head2 exists() is supported on subroutine names
1090
1091The exists() builtin now works on subroutine names. A subroutine
1092is considered to exist if it has been declared (even if implicitly).
1093See L<perlfunc/exists> for examples.
1094
1095=head2 exists() and delete() are supported on array elements
1096
1097The exists() and delete() builtins now work on simple arrays as well.
1098The behavior is similar to that on hash elements.
1099
1100exists() can be used to check whether an array element has been
1101initialized. This avoids autovivifying array elements that don't exist.
1102If the array is tied, the EXISTS() method in the corresponding tied
1103package will be invoked.
1104
1105delete() may be used to remove an element from the array and return
1106it. The array element at that position returns to its uninitialized
1107state, so that testing for the same element with exists() will return
1108false. If the element happens to be the one at the end, the size of
1109the array also shrinks up to the highest element that tests true for
1110exists(), or 0 if none such is found. If the array is tied, the DELETE()
1111method in the corresponding tied package will be invoked.
1112
1113See L<perlfunc/exists> and L<perlfunc/delete> for examples.
1114
1115=head2 Pseudo-hashes work better
1116
1117Dereferencing some types of reference values in a pseudo-hash,
1118such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
1119been corrected.
1120
1121When applied to a pseudo-hash element, exists() now reports whether
1122the specified value exists, not merely if the key is valid.
1123
1124delete() now works on pseudo-hashes. When given a pseudo-hash element
1125or slice it deletes the values corresponding to the keys (but not the keys
1126themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1127
1128Pseudo-hash slices with constant keys are now optimized to array lookups
1129at compile-time.
1130
1131List assignments to pseudo-hash slices are now supported.
1132
1133The C<fields> pragma now provides ways to create pseudo-hashes, via
1134fields::new() and fields::phash(). See L<fields>.
1135
1136 NOTE: The pseudo-hash data type continues to be experimental.
1137 Limiting oneself to the interface elements provided by the
1138 fields pragma will provide protection from any future changes.
1139
1140=head2 Automatic flushing of output buffers
1141
1142fork(), exec(), system(), qx//, and pipe open()s now flush buffers
1143of all files opened for output when the operation was attempted. This
1144mostly eliminates confusing buffering mishaps suffered by users unaware
1145of how Perl internally handles I/O.
1146
1147This is not supported on some platforms like Solaris where a suitably
1148correct implementation of fflush(NULL) isn't available.
1149
1150=head2 Better diagnostics on meaningless filehandle operations
1151
1152Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
1153are compile time errors. Attempting to read from filehandles that
1154were opened only for writing will now produce warnings (just as
1155writing to read-only filehandles does).
1156
1157=head2 Where possible, buffered data discarded from duped input filehandle
1158
1159C<< open(NEW, "<&OLD") >> now attempts to discard any data that
1160was previously read and buffered in C<OLD> before duping the handle.
1161On platforms where doing this is allowed, the next read operation
1162on C<NEW> will return the same data as the corresponding operation
1163on C<OLD>. Formerly, it would have returned the data from the start
1164of the following disk block instead.
1165
1166=head2 eof() has the same old magic as <>
1167
1168C<eof()> would return true if no attempt to read from C<< <> >> had
1169yet been made. C<eof()> has been changed to have a little magic of its
1170own, it now opens the C<< <> >> files.
1171
1172=head2 binmode() can be used to set :crlf and :raw modes
1173
1174binmode() now accepts a second argument that specifies a discipline
1175for the handle in question. The two pseudo-disciplines ":raw" and
1176":crlf" are currently supported on DOS-derivative platforms.
1177See L<perlfunc/"binmode"> and L<open>.
1178
1179=head2 C<-T> filetest recognizes UTF-8 encoded files as "text"
1180
1181The algorithm used for the C<-T> filetest has been enhanced to
1182correctly identify UTF-8 content as "text".
1183
1184=head2 system(), backticks and pipe open now reflect exec() failure
1185
1186On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1187etc., are implemented via fork() and exec(). When the underlying
1188exec() fails, earlier versions did not report the error properly,
1189since the exec() happened to be in a different process.
1190
1191The child process now communicates with the parent about the
1192error in launching the external command, which allows these
1193constructs to return with their usual error value and set $!.
1194
1195=head2 Improved diagnostics
1196
1197Line numbers are no longer suppressed (under most likely circumstances)
1198during the global destruction phase.
1199
1200Diagnostics emitted from code running in threads other than the main
1201thread are now accompanied by the thread ID.
1202
1203Embedded null characters in diagnostics now actually show up. They
1204used to truncate the message in prior versions.
1205
1206$foo::a and $foo::b are now exempt from "possible typo" warnings only
1207if sort() is encountered in package C<foo>.
1208
1209Unrecognized alphabetic escapes encountered when parsing quote
1210constructs now generate a warning, since they may take on new
1211semantics in later versions of Perl.
1212
1213Many diagnostics now report the internal operation in which the warning
1214was provoked, like so:
1215
1216 Use of uninitialized value in concatenation (.) at (eval 1) line 1.
1217 Use of uninitialized value in print at (eval 1) line 1.
1218
1219Diagnostics that occur within eval may also report the file and line
1220number where the eval is located, in addition to the eval sequence
1221number and the line number within the evaluated text itself. For
1222example:
1223
1224 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
1225
1226=head2 Diagnostics follow STDERR
1227
1228Diagnostic output now goes to whichever file the C<STDERR> handle
1229is pointing at, instead of always going to the underlying C runtime
1230library's C<stderr>.
1231
1232=head2 More consistent close-on-exec behavior
1233
1234On systems that support a close-on-exec flag on filehandles, the
1235flag is now set for any handles created by pipe(), socketpair(),
1236socket(), and accept(), if that is warranted by the value of $^F
1237that may be in effect. Earlier versions neglected to set the flag
1238for handles created with these operators. See L<perlfunc/pipe>,
1239L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
1240and L<perlvar/$^F>.
1241
1242=head2 syswrite() ease-of-use
1243
1244The length argument of C<syswrite()> has become optional.
1245
1246=head2 Better syntax checks on parenthesized unary operators
1247
1248Expressions such as:
1249
1250 print defined(&foo,&bar,&baz);
1251 print uc("foo","bar","baz");
1252 undef($foo,&bar);
1253
1254used to be accidentally allowed in earlier versions, and produced
1255unpredictable behaviour. Some produced ancillary warnings
1256when used in this way; others silently did the wrong thing.
1257
1258The parenthesized forms of most unary operators that expect a single
1259argument now ensure that they are not called with more than one
1260argument, making the cases shown above syntax errors. The usual
1261behaviour of:
1262
1263 print defined &foo, &bar, &baz;
1264 print uc "foo", "bar", "baz";
1265 undef $foo, &bar;
1266
1267remains unchanged. See L<perlop>.
1268
1269=head2 Bit operators support full native integer width
1270
1271The bit operators (& | ^ ~ << >>) now operate on the full native
1272integral width (the exact size of which is available in $Config{ivsize}).
1273For example, if your platform is either natively 64-bit or if Perl
1274has been configured to use 64-bit integers, these operations apply
1275to 8 bytes (as opposed to 4 bytes on 32-bit platforms).
1276For portability, be sure to mask off the excess bits in the result of
1277unary C<~>, e.g., C<~$x & 0xffffffff>.
1278
1279=head2 Improved security features
1280
1281More potentially unsafe operations taint their results for improved
1282security.
1283
1284The C<passwd> and C<shell> fields returned by the getpwent(), getpwnam(),
1285and getpwuid() are now tainted, because the user can affect their own
1286encrypted password and login shell.
1287
1288The variable modified by shmread(), and messages returned by msgrcv()
1289(and its object-oriented interface IPC::SysV::Msg::rcv) are also tainted,
1290because other untrusted processes can modify messages and shared memory
1291segments for their own nefarious purposes.
1292
1293=head2 More functional bareword prototype (*)
1294
1295Bareword prototypes have been rationalized to enable them to be used
1296to override builtins that accept barewords and interpret them in
1297a special way, such as C<require> or C<do>.
1298
1299Arguments prototyped as C<*> will now be visible within the subroutine
1300as either a simple scalar or as a reference to a typeglob.
1301See L<perlsub/Prototypes>.
1302
1303=head2 C<require> and C<do> may be overridden
1304
1305C<require> and C<do 'file'> operations may be overridden locally
1306by importing subroutines of the same name into the current package
1307(or globally by importing them into the CORE::GLOBAL:: namespace).
1308Overriding C<require> will also affect C<use>, provided the override
1309is visible at compile-time.
1310See L<perlsub/"Overriding Built-in Functions">.
1311
1312=head2 $^X variables may now have names longer than one character
1313
1314Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
1315error. Now variable names that begin with a control character may be
1316arbitrarily long. However, for compatibility reasons, these variables
1317I<must> be written with explicit braces, as C<${^XY}> for example.
1318C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
1319than one control character, such as C<${^XY^Z}>, are illegal.
1320
1321The old syntax has not changed. As before, `^X' may be either a
1322literal control-X character or the two-character sequence `caret' plus
1323`X'. When braces are omitted, the variable name stops after the
1324control character. Thus C<"$^XYZ"> continues to be synonymous with
1325C<$^X . "YZ"> as before.
1326
1327As before, lexical variables may not have names beginning with control
1328characters. As before, variables whose names begin with a control
1329character are always forced to be in package `main'. All such variables
1330are reserved for future extensions, except those that begin with
1331C<^_>, which may be used by user programs and are guaranteed not to
1332acquire special meaning in any future version of Perl.
1333
1334=head2 New variable $^C reflects C<-c> switch
1335
1336C<$^C> has a boolean value that reflects whether perl is being run
1337in compile-only mode (i.e. via the C<-c> switch). Since
1338BEGIN blocks are executed under such conditions, this variable
1339enables perl code to determine whether actions that make sense
1340only during normal running are warranted. See L<perlvar>.
1341
1342=head2 New variable $^V contains Perl version as a string
1343
1344C<$^V> contains the Perl version number as a string composed of
1345characters whose ordinals match the version numbers, i.e. v5.6.0.
1346This may be used in string comparisons.
1347
1348See C<Support for strings represented as a vector of ordinals> for an
1349example.
1350
1351=head2 Optional Y2K warnings
1352
1353If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
1354it emits optional warnings when concatenating the number 19
1355with another number.
1356
1357This behavior must be specifically enabled when running Configure.
1358See F<INSTALL> and F<README.Y2K>.
1359
1360=head2 Arrays now always interpolate into double-quoted strings
1361
1362In double-quoted strings, arrays now interpolate, no matter what. The
1363behavior in earlier versions of perl 5 was that arrays would interpolate
1364into strings if the array had been mentioned before the string was
1365compiled, and otherwise Perl would raise a fatal compile-time error.
1366In versions 5.000 through 5.003, the error was
1367
1368 Literal @example now requires backslash
1369
1370In versions 5.004_01 through 5.6.0, the error was
1371
1372 In string, @example now must be written as \@example
1373
1374The idea here was to get people into the habit of writing
1375C<"fred\@example.com"> when they wanted a literal C<@> sign, just as
1376they have always written C<"Give me back my \$5"> when they wanted a
1377literal C<$> sign.
1378
1379Starting with 5.6.1, when Perl now sees an C<@> sign in a
1380double-quoted string, it I<always> attempts to interpolate an array,
1381regardless of whether or not the array has been used or declared
1382already. The fatal error has been downgraded to an optional warning:
1383
1384 Possible unintended interpolation of @example in string
1385
1386This warns you that C<"fred@example.com"> is going to turn into
1387C<fred.com> if you don't backslash the C<@>.
08d7a6b2 1388See http://perl.plover.com/at-error.html for more details
493a87da
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1389about the history here.
1390
3e4c7cf0
YST
1391=head2 @- and @+ provide starting/ending offsets of regex submatches
1392
1393The new magic variables @- and @+ provide the starting and ending
1394offsets, respectively, of $&, $1, $2, etc. See L<perlvar> for
1395details.
1396
493a87da
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1397=head1 Modules and Pragmata
1398
1399=head2 Modules
1400
1401=over 4
1402
1403=item attributes
1404
1405While used internally by Perl as a pragma, this module also
1406provides a way to fetch subroutine and variable attributes.
1407See L<attributes>.
1408
1409=item B
1410
1411The Perl Compiler suite has been extensively reworked for this
353c6505 1412release. More of the standard Perl test suite passes when run
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1413under the Compiler, but there is still a significant way to
1414go to achieve production quality compiled executables.
1415
1416 NOTE: The Compiler suite remains highly experimental. The
1417 generated code may not be correct, even when it manages to execute
1418 without errors.
1419
1420=item Benchmark
1421
1422Overall, Benchmark results exhibit lower average error and better timing
1423accuracy.
1424
1425You can now run tests for I<n> seconds instead of guessing the right
1426number of tests to run: e.g., timethese(-5, ...) will run each
1427code for at least 5 CPU seconds. Zero as the "number of repetitions"
1428means "for at least 3 CPU seconds". The output format has also
1429changed. For example:
1430
1431 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1432
1433will now output something like this:
1434
1435 Benchmark: running a, b, each for at least 5 CPU seconds...
1436 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1437 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1438
1439New features: "each for at least N CPU seconds...", "wallclock secs",
1440and the "@ operations/CPU second (n=operations)".
1441
1442timethese() now returns a reference to a hash of Benchmark objects containing
1443the test results, keyed on the names of the tests.
1444
1445timethis() now returns the iterations field in the Benchmark result object
1446instead of 0.
1447
1448timethese(), timethis(), and the new cmpthese() (see below) can also take
1449a format specifier of 'none' to suppress output.
1450
1451A new function countit() is just like timeit() except that it takes a
1452TIME instead of a COUNT.
1453
1454A new function cmpthese() prints a chart comparing the results of each test
1455returned from a timethese() call. For each possible pair of tests, the
1456percentage speed difference (iters/sec or seconds/iter) is shown.
1457
1458For other details, see L<Benchmark>.
1459
1460=item ByteLoader
1461
1462The ByteLoader is a dedicated extension to generate and run
1463Perl bytecode. See L<ByteLoader>.
1464
1465=item constant
1466
1467References can now be used.
1468
1469The new version also allows a leading underscore in constant names, but
1470disallows a double leading underscore (as in "__LINE__"). Some other names
1471are disallowed or warned against, including BEGIN, END, etc. Some names
1472which were forced into main:: used to fail silently in some cases; now they're
1473fatal (outside of main::) and an optional warning (inside of main::).
1474The ability to detect whether a constant had been set with a given name has
1475been added.
1476
1477See L<constant>.
1478
1479=item charnames
1480
1481This pragma implements the C<\N> string escape. See L<charnames>.
1482
1483=item Data::Dumper
1484
1485A C<Maxdepth> setting can be specified to avoid venturing
1486too deeply into deep data structures. See L<Data::Dumper>.
1487
1488The XSUB implementation of Dump() is now automatically called if the
1489C<Useqq> setting is not in use.
1490
1491Dumping C<qr//> objects works correctly.
1492
1493=item DB
1494
1495C<DB> is an experimental module that exposes a clean abstraction
1496to Perl's debugging API.
1497
1498=item DB_File
1499
1500DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1501See C<ext/DB_File/Changes>.
1502
1503=item Devel::DProf
1504
1505Devel::DProf, a Perl source code profiler has been added. See
1506L<Devel::DProf> and L<dprofpp>.
1507
1508=item Devel::Peek
1509
1510The Devel::Peek module provides access to the internal representation
1511of Perl variables and data. It is a data debugging tool for the XS programmer.
1512
1513=item Dumpvalue
1514
1515The Dumpvalue module provides screen dumps of Perl data.
1516
1517=item DynaLoader
1518
1519DynaLoader now supports a dl_unload_file() function on platforms that
1520support unloading shared objects using dlclose().
1521
1522Perl can also optionally arrange to unload all extension shared objects
1523loaded by Perl. To enable this, build Perl with the Configure option
1524C<-Accflags=-DDL_UNLOAD_ALL_AT_EXIT>. (This maybe useful if you are
1525using Apache with mod_perl.)
1526
1527=item English
1528
1529$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1530(a numeric value).
1531
1532=item Env
1533
1534Env now supports accessing environment variables like PATH as array
1535variables.
1536
1537=item Fcntl
1538
1539More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1540large file (more than 4GB) access (NOTE: the O_LARGEFILE is
1541automatically added to sysopen() flags if large file support has been
1542configured, as is the default), Free/Net/OpenBSD locking behaviour
1543flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
1544mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek()
1545constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
1546C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions
1547are available via the C<:mode> tag.
1548
1549=item File::Compare
1550
1551A compare_text() function has been added, which allows custom
1552comparison functions. See L<File::Compare>.
1553
1554=item File::Find
1555
1556File::Find now works correctly when the wanted() function is either
1557autoloaded or is a symbolic reference.
1558
1559A bug that caused File::Find to lose track of the working directory
1560when pruning top-level directories has been fixed.
1561
1562File::Find now also supports several other options to control its
1563behavior. It can follow symbolic links if the C<follow> option is
1564specified. Enabling the C<no_chdir> option will make File::Find skip
1565changing the current directory when walking directories. The C<untaint>
1566flag can be useful when running with taint checks enabled.
1567
1568See L<File::Find>.
1569
1570=item File::Glob
1571
1572This extension implements BSD-style file globbing. By default,
1573it will also be used for the internal implementation of the glob()
1574operator. See L<File::Glob>.
1575
1576=item File::Spec
1577
1578New methods have been added to the File::Spec module: devnull() returns
1579the name of the null device (/dev/null on Unix) and tmpdir() the name of
1580the temp directory (normally /tmp on Unix). There are now also methods
1581to convert between absolute and relative filenames: abs2rel() and
1582rel2abs(). For compatibility with operating systems that specify volume
1583names in file paths, the splitpath(), splitdir(), and catdir() methods
1584have been added.
1585
1586=item File::Spec::Functions
1587
1588The new File::Spec::Functions modules provides a function interface
1589to the File::Spec module. Allows shorthand
1590
1591 $fullname = catfile($dir1, $dir2, $file);
1592
1593instead of
1594
1595 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1596
1597=item Getopt::Long
1598
1599Getopt::Long licensing has changed to allow the Perl Artistic License
1600as well as the GPL. It used to be GPL only, which got in the way of
1601non-GPL applications that wanted to use Getopt::Long.
1602
1603Getopt::Long encourages the use of Pod::Usage to produce help
1604messages. For example:
1605
1606 use Getopt::Long;
1607 use Pod::Usage;
1608 my $man = 0;
1609 my $help = 0;
1610 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1611 pod2usage(1) if $help;
1612 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1613
1614 __END__
1615
1616 =head1 NAME
1617
fe854a6f 1618 sample - Using Getopt::Long and Pod::Usage
493a87da
JH
1619
1620 =head1 SYNOPSIS
1621
1622 sample [options] [file ...]
1623
1624 Options:
1625 -help brief help message
1626 -man full documentation
1627
1628 =head1 OPTIONS
1629
1630 =over 8
1631
1632 =item B<-help>
1633
1634 Print a brief help message and exits.
1635
1636 =item B<-man>
1637
1638 Prints the manual page and exits.
1639
1640 =back
1641
1642 =head1 DESCRIPTION
1643
1644 B<This program> will read the given input file(s) and do something
1645 useful with the contents thereof.
1646
1647 =cut
1648
1649See L<Pod::Usage> for details.
1650
1651A bug that prevented the non-option call-back <> from being
1652specified as the first argument has been fixed.
1653
1654To specify the characters < and > as option starters, use ><. Note,
1655however, that changing option starters is strongly deprecated.
1656
1657=item IO
1658
1659write() and syswrite() will now accept a single-argument
1660form of the call, for consistency with Perl's syswrite().
1661
1662You can now create a TCP-based IO::Socket::INET without forcing
1663a connect attempt. This allows you to configure its options
1664(like making it non-blocking) and then call connect() manually.
1665
1666A bug that prevented the IO::Socket::protocol() accessor
1667from ever returning the correct value has been corrected.
1668
1669IO::Socket::connect now uses non-blocking IO instead of alarm()
1670to do connect timeouts.
1671
1672IO::Socket::accept now uses select() instead of alarm() for doing
1673timeouts.
1674
1675IO::Socket::INET->new now sets $! correctly on failure. $@ is
1676still set for backwards compatibility.
1677
1678=item JPL
1679
1680Java Perl Lingo is now distributed with Perl. See jpl/README
1681for more information.
1682
1683=item lib
1684
1685C<use lib> now weeds out any trailing duplicate entries.
1686C<no lib> removes all named entries.
1687
1688=item Math::BigInt
1689
1690The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
1691and C<~> are now supported on bigints.
1692
1693=item Math::Complex
1694
1695The accessor methods Re, Im, arg, abs, rho, and theta can now also
1696act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1697
1698The class method C<display_format> and the corresponding object method
1699C<display_format>, in addition to accepting just one argument, now can
1700also accept a parameter hash. Recognized keys of a parameter hash are
1701C<"style">, which corresponds to the old one parameter case, and two
1702new parameters: C<"format">, which is a printf()-style format string
1703(defaults usually to C<"%.15g">, you can revert to the default by
1704setting the format string to C<undef>) used for both parts of a
1705complex number, and C<"polar_pretty_print"> (defaults to true),
1706which controls whether an attempt is made to try to recognize small
1707multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
1708polar complex number.
1709
1710The potentially disruptive change is that in list context both methods
1711now I<return the parameter hash>, instead of only the value of the
1712C<"style"> parameter.
1713
1714=item Math::Trig
1715
1716A little bit of radial trigonometry (cylindrical and spherical),
1717radial coordinate conversions, and the great circle distance were added.
1718
1719=item Pod::Parser, Pod::InputObjects
1720
1721Pod::Parser is a base class for parsing and selecting sections of
1722pod documentation from an input stream. This module takes care of
1723identifying pod paragraphs and commands in the input and hands off the
1724parsed paragraphs and commands to user-defined methods which are free
1725to interpret or translate them as they see fit.
1726
1727Pod::InputObjects defines some input objects needed by Pod::Parser, and
1728for advanced users of Pod::Parser that need more about a command besides
1729its name and text.
1730
1731As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
1732"base parser code" recommended for use by all pod2xxx translators.
1733Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1734to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1735underway. For any questions or comments about pod parsing and translating
1736issues and utilities, please use the pod-people@perl.org mailing list.
1737
1738For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1739
1740=item Pod::Checker, podchecker
1741
1742This utility checks pod files for correct syntax, according to
1743L<perlpod>. Obvious errors are flagged as such, while warnings are
1744printed for mistakes that can be handled gracefully. The checklist is
1745not complete yet. See L<Pod::Checker>.
1746
1747=item Pod::ParseUtils, Pod::Find
1748
1749These modules provide a set of gizmos that are useful mainly for pod
1750translators. L<Pod::Find|Pod::Find> traverses directory structures and
1751returns found pod files, along with their canonical names (like
1752C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1753B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1754(for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
1755(for caching information about pod files, e.g., link nodes).
1756
1757=item Pod::Select, podselect
1758
1759Pod::Select is a subclass of Pod::Parser which provides a function
1760named "podselect()" to filter out user-specified sections of raw pod
1761documentation from an input stream. podselect is a script that provides
1762access to Pod::Select from other scripts to be used as a filter.
1763See L<Pod::Select>.
1764
1765=item Pod::Usage, pod2usage
1766
1767Pod::Usage provides the function "pod2usage()" to print usage messages for
1768a Perl script based on its embedded pod documentation. The pod2usage()
1769function is generally useful to all script authors since it lets them
1770write and maintain a single source (the pods) for documentation, thus
1771removing the need to create and maintain redundant usage message text
1772consisting of information already in the pods.
1773
1774There is also a pod2usage script which can be used from other kinds of
1775scripts to print usage messages from pods (even for non-Perl scripts
1776with pods embedded in comments).
1777
1778For details and examples, please see L<Pod::Usage>.
1779
1780=item Pod::Text and Pod::Man
1781
1782Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
1783still available for backwards compatibility, the module now has a new
1784preferred interface. See L<Pod::Text> for the details. The new Pod::Text
1785module is easily subclassed for tweaks to the output, and two such
1786subclasses (Pod::Text::Termcap for man-page-style bold and underlining
1787using termcap information, and Pod::Text::Color for markup with ANSI color
1788sequences) are now standard.
1789
1790pod2man has been turned into a module, Pod::Man, which also uses
1791Pod::Parser. In the process, several outstanding bugs related to quotes
1792in section headers, quoting of code escapes, and nested lists have been
1793fixed. pod2man is now a wrapper script around this module.
1794
1795=item SDBM_File
1796
1797An EXISTS method has been added to this module (and sdbm_exists() has
1798been added to the underlying sdbm library), so one can now call exists
1799on an SDBM_File tied hash and get the correct result, rather than a
1800runtime error.
1801
1802A bug that may have caused data loss when more than one disk block
1803happens to be read from the database in a single FETCH() has been
1804fixed.
1805
1806=item Sys::Syslog
1807
1808Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1809no longer requires syslog.ph to exist.
1810
1811=item Sys::Hostname
1812
1813Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1814uname() if they exist.
1815
1816=item Term::ANSIColor
1817
1818Term::ANSIColor is a very simple module to provide easy and readable
1819access to the ANSI color and highlighting escape sequences, supported by
1820most ANSI terminal emulators. It is now included standard.
1821
1822=item Time::Local
1823
1824The timelocal() and timegm() functions used to silently return bogus
1825results when the date fell outside the machine's integer range. They
1826now consistently croak() if the date falls in an unsupported range.
1827
1828=item Win32
1829
1830The error return value in list context has been changed for all functions
1831that return a list of values. Previously these functions returned a list
1832with a single element C<undef> if an error occurred. Now these functions
1833return the empty list in these situations. This applies to the following
1834functions:
1835
1836 Win32::FsType
1837 Win32::GetOSVersion
1838
1839The remaining functions are unchanged and continue to return C<undef> on
1840error even in list context.
1841
1842The Win32::SetLastError(ERROR) function has been added as a complement
1843to the Win32::GetLastError() function.
1844
1845The new Win32::GetFullPathName(FILENAME) returns the full absolute
1846pathname for FILENAME in scalar context. In list context it returns
1847a two-element list containing the fully qualified directory name and
1848the filename. See L<Win32>.
1849
1850=item XSLoader
1851
1852The XSLoader extension is a simpler alternative to DynaLoader.
1853See L<XSLoader>.
1854
1855=item DBM Filters
1856
1857A new feature called "DBM Filters" has been added to all the
1858DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1859DBM Filters add four new methods to each DBM module:
1860
1861 filter_store_key
1862 filter_store_value
1863 filter_fetch_key
1864 filter_fetch_value
1865
1866These can be used to filter key-value pairs before the pairs are
1867written to the database or just after they are read from the database.
1868See L<perldbmfilter> for further information.
1869
1870=back
1871
1872=head2 Pragmata
1873
1874C<use attrs> is now obsolete, and is only provided for
1875backward-compatibility. It's been replaced by the C<sub : attributes>
1876syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1877
1878Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1879See L<perllexwarn>.
1880
1881C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1882...). Currently only one subpragma implemented, "use filetest
1883'access';", that uses access(2) or equivalent to check permissions
1884instead of using stat(2) as usual. This matters in filesystems
1885where there are ACLs (access control lists): the stat(2) might lie,
1886but access(2) knows better.
1887
1888The C<open> pragma can be used to specify default disciplines for
1889handle constructors (e.g. open()) and for qx//. The two
1890pseudo-disciplines C<:raw> and C<:crlf> are currently supported on
1891DOS-derivative platforms (i.e. where binmode is not a no-op).
1892See also L</"binmode() can be used to set :crlf and :raw modes">.
1893
1894=head1 Utility Changes
1895
1896=head2 dprofpp
1897
1898C<dprofpp> is used to display profile data generated using C<Devel::DProf>.
1899See L<dprofpp>.
1900
1901=head2 find2perl
1902
1903The C<find2perl> utility now uses the enhanced features of the File::Find
1904module. The -depth and -follow options are supported. Pod documentation
1905is also included in the script.
1906
1907=head2 h2xs
1908
1909The C<h2xs> tool can now work in conjunction with C<C::Scan> (available
1910from CPAN) to automatically parse real-life header files. The C<-M>,
1911C<-a>, C<-k>, and C<-o> options are new.
1912
1913=head2 perlcc
1914
1915C<perlcc> now supports the C and Bytecode backends. By default,
1916it generates output from the simple C backend rather than the
1917optimized C backend.
1918
1919Support for non-Unix platforms has been improved.
1920
1921=head2 perldoc
1922
1923C<perldoc> has been reworked to avoid possible security holes.
1924It will not by default let itself be run as the superuser, but you
1925may still use the B<-U> switch to try to make it drop privileges
1926first.
1927
1928=head2 The Perl Debugger
1929
1930Many bug fixes and enhancements were added to F<perl5db.pl>, the
1931Perl debugger. The help documentation was rearranged. New commands
1932include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current
1933actions, C<man I<docpage>> to run your doc viewer on some perl
1934docset, and support for quoted options. The help information was
1935rearranged, and should be viewable once again if you're using B<less>
1936as your pager. A serious security hole was plugged--you should
1937immediately remove all older versions of the Perl debugger as
1938installed in previous releases, all the way back to perl3, from
1939your system to avoid being bitten by this.
1940
1941=head1 Improved Documentation
1942
1943Many of the platform-specific README files are now part of the perl
1944installation. See L<perl> for the complete list.
1945
1946=over 4
1947
1948=item perlapi.pod
1949
1950The official list of public Perl API functions.
1951
1952=item perlboot.pod
1953
1954A tutorial for beginners on object-oriented Perl.
1955
1956=item perlcompile.pod
1957
1958An introduction to using the Perl Compiler suite.
1959
1960=item perldbmfilter.pod
1961
1962A howto document on using the DBM filter facility.
1963
1964=item perldebug.pod
1965
1966All material unrelated to running the Perl debugger, plus all
1967low-level guts-like details that risked crushing the casual user
1968of the debugger, have been relocated from the old manpage to the
1969next entry below.
1970
1971=item perldebguts.pod
1972
1973This new manpage contains excessively low-level material not related
1974to the Perl debugger, but slightly related to debugging Perl itself.
1975It also contains some arcane internal details of how the debugging
1976process works that may only be of interest to developers of Perl
1977debuggers.
1978
1979=item perlfork.pod
1980
1981Notes on the fork() emulation currently available for the Windows platform.
1982
1983=item perlfilter.pod
1984
1985An introduction to writing Perl source filters.
1986
1987=item perlhack.pod
1988
1989Some guidelines for hacking the Perl source code.
1990
1991=item perlintern.pod
1992
1993A list of internal functions in the Perl source code.
1994(List is currently empty.)
1995
1996=item perllexwarn.pod
1997
1998Introduction and reference information about lexically scoped
1999warning categories.
2000
2001=item perlnumber.pod
2002
2003Detailed information about numbers as they are represented in Perl.
2004
2005=item perlopentut.pod
2006
2007A tutorial on using open() effectively.
2008
2009=item perlreftut.pod
2010
2011A tutorial that introduces the essentials of references.
2012
2013=item perltootc.pod
2014
2015A tutorial on managing class data for object modules.
2016
2017=item perltodo.pod
2018
2019Discussion of the most often wanted features that may someday be
2020supported in Perl.
2021
2022=item perlunicode.pod
2023
2024An introduction to Unicode support features in Perl.
2025
2026=back
2027
2028=head1 Performance enhancements
2029
2030=head2 Simple sort() using { $a <=> $b } and the like are optimized
2031
2032Many common sort() operations using a simple inlined block are now
2033optimized for faster performance.
2034
2035=head2 Optimized assignments to lexical variables
2036
2037Certain operations in the RHS of assignment statements have been
2038optimized to directly set the lexical variable on the LHS,
2039eliminating redundant copying overheads.
2040
2041=head2 Faster subroutine calls
2042
2043Minor changes in how subroutine calls are handled internally
2044provide marginal improvements in performance.
2045
2046=head2 delete(), each(), values() and hash iteration are faster
2047
2048The hash values returned by delete(), each(), values() and hashes in a
2049list context are the actual values in the hash, instead of copies.
2050This results in significantly better performance, because it eliminates
2051needless copying in most situations.
2052
2053=head1 Installation and Configuration Improvements
2054
2055=head2 -Dusethreads means something different
2056
2057The -Dusethreads flag now enables the experimental interpreter-based thread
2058support by default. To get the flavor of experimental threads that was in
20595.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
2060
2061As of v5.6.0, interpreter-threads support is still lacking a way to
2062create new threads from Perl (i.e., C<use Thread;> will not work with
2063interpreter threads). C<use Thread;> continues to be available when you
2064specify the -Duse5005threads option to Configure, bugs and all.
2065
2066 NOTE: Support for threads continues to be an experimental feature.
2067 Interfaces and implementation are subject to sudden and drastic changes.
2068
2069=head2 New Configure flags
2070
2071The following new flags may be enabled on the Configure command line
2072by running Configure with C<-Dflag>.
2073
2074 usemultiplicity
2075 usethreads useithreads (new interpreter threads: no Perl API yet)
2076 usethreads use5005threads (threads as they were in 5.005)
2077
2078 use64bitint (equal to now deprecated 'use64bits')
2079 use64bitall
2080
2081 uselongdouble
2082 usemorebits
2083 uselargefiles
2084 usesocks (only SOCKS v5 supported)
2085
2086=head2 Threadedness and 64-bitness now more daring
2087
2088The Configure options enabling the use of threads and the use of
208964-bitness are now more daring in the sense that they no more have an
2090explicit list of operating systems of known threads/64-bit
2091capabilities. In other words: if your operating system has the
2092necessary APIs and datatypes, you should be able just to go ahead and
2093use them, for threads by Configure -Dusethreads, and for 64 bits
2094either explicitly by Configure -Duse64bitint or implicitly if your
2095system has 64-bit wide datatypes. See also L<"64-bit support">.
2096
2097=head2 Long Doubles
2098
2099Some platforms have "long doubles", floating point numbers of even
2100larger range than ordinary "doubles". To enable using long doubles for
2101Perl's scalars, use -Duselongdouble.
2102
2103=head2 -Dusemorebits
2104
2105You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
2106See also L<"64-bit support">.
2107
2108=head2 -Duselargefiles
2109
2110Some platforms support system APIs that are capable of handling large files
2111(typically, files larger than two gigabytes). Perl will try to use these
2112APIs if you ask for -Duselargefiles.
2113
2114See L<"Large file support"> for more information.
2115
2116=head2 installusrbinperl
2117
2118You can use "Configure -Uinstallusrbinperl" which causes installperl
2119to skip installing perl also as /usr/bin/perl. This is useful if you
2120prefer not to modify /usr/bin for some reason or another but harmful
2121because many scripts assume to find Perl in /usr/bin/perl.
2122
2123=head2 SOCKS support
2124
2125You can use "Configure -Dusesocks" which causes Perl to probe
2126for the SOCKS proxy protocol library (v5, not v4). For more information
2127on SOCKS, see:
2128
2129 http://www.socks.nec.com/
2130
2131=head2 C<-A> flag
2132
2133You can "post-edit" the Configure variables using the Configure C<-A>
2134switch. The editing happens immediately after the platform specific
2135hints files have been processed but before the actual configuration
2136process starts. Run C<Configure -h> to find out the full C<-A> syntax.
2137
2138=head2 Enhanced Installation Directories
2139
2140The installation structure has been enriched to improve the support
2141for maintaining multiple versions of perl, to provide locations for
2142vendor-supplied modules, scripts, and manpages, and to ease maintenance
2143of locally-added modules, scripts, and manpages. See the section on
2144Installation Directories in the INSTALL file for complete details.
2145For most users building and installing from source, the defaults should
2146be fine.
2147
2148If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
2149special values for library directories, you might wish to consider using
2150the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
2151config.sh file from an earlier version of perl, you should be sure to
2152check that Configure makes sensible choices for the new directories.
2153See INSTALL for complete details.
2154
2155=head2 gcc automatically tried if 'cc' does not seem to be working
2156
2157In many platforms the vendor-supplied 'cc' is too stripped-down to
2158build Perl (basically, the 'cc' doesn't do ANSI C). If this seems
2159to be the case and the 'cc' does not seem to be the GNU C compiler
2160'gcc', an automatic attempt is made to find and use 'gcc' instead.
2161
2162=head1 Platform specific changes
2163
2164=head2 Supported platforms
2165
2166=over 4
2167
2168=item *
2169
2170The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
2171extension.
2172
2173=item *
2174
2175GNU/Hurd is now supported.
2176
2177=item *
2178
2179Rhapsody/Darwin is now supported.
2180
2181=item *
2182
2183EPOC is now supported (on Psion 5).
2184
2185=item *
2186
2187The cygwin port (formerly cygwin32) has been greatly improved.
2188
2189=back
2190
2191=head2 DOS
2192
2193=over 4
2194
2195=item *
2196
2197Perl now works with djgpp 2.02 (and 2.03 alpha).
2198
2199=item *
2200
2201Environment variable names are not converted to uppercase any more.
2202
2203=item *
2204
2205Incorrect exit codes from backticks have been fixed.
2206
2207=item *
2208
2209This port continues to use its own builtin globbing (not File::Glob).
2210
2211=back
2212
2213=head2 OS390 (OpenEdition MVS)
2214
2215Support for this EBCDIC platform has not been renewed in this release.
2216There are difficulties in reconciling Perl's standardization on UTF-8
2217as its internal representation for characters with the EBCDIC character
2218set, because the two are incompatible.
2219
2220It is unclear whether future versions will renew support for this
2221platform, but the possibility exists.
2222
2223=head2 VMS
2224
2225Numerous revisions and extensions to configuration, build, testing, and
2226installation process to accommodate core changes and VMS-specific options.
2227
2228Expand %ENV-handling code to allow runtime mapping to logical names,
2229CLI symbols, and CRTL environ array.
2230
2231Extension of subprocess invocation code to accept filespecs as command
2232"verbs".
2233
2234Add to Perl command line processing the ability to use default file types and
2235to recognize Unix-style C<2E<gt>&1>.
2236
2237Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.
2238
2239Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.
2240
2241Barewords at start of Unix-syntax paths may be treated as text rather than
2242only as logical names.
2243
2244Optional secure translation of several logical names used internally by Perl.
2245
2246Miscellaneous bugfixing and porting of new core code to VMS.
2247
2248Thanks are gladly extended to the many people who have contributed VMS
2249patches, testing, and ideas.
2250
2251=head2 Win32
2252
2253Perl can now emulate fork() internally, using multiple interpreters running
2254in different concurrent threads. This support must be enabled at build
2255time. See L<perlfork> for detailed information.
2256
2257When given a pathname that consists only of a drivename, such as C<A:>,
2258opendir() and stat() now use the current working directory for the drive
2259rather than the drive root.
2260
2261The builtin XSUB functions in the Win32:: namespace are documented. See
2262L<Win32>.
2263
2264$^X now contains the full path name of the running executable.
2265
2266A Win32::GetLongPathName() function is provided to complement
2267Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
2268
2269POSIX::uname() is supported.
2270
2271system(1,...) now returns true process IDs rather than process
2272handles. kill() accepts any real process id, rather than strictly
2273return values from system(1,...).
2274
2275For better compatibility with Unix, C<kill(0, $pid)> can now be used to
2276test whether a process exists.
2277
2278The C<Shell> module is supported.
2279
2280Better support for building Perl under command.com in Windows 95
2281has been added.
2282
2283Scripts are read in binary mode by default to allow ByteLoader (and
2284the filter mechanism in general) to work properly. For compatibility,
2285the DATA filehandle will be set to text mode if a carriage return is
2286detected at the end of the line containing the __END__ or __DATA__
2287token; if not, the DATA filehandle will be left open in binary mode.
2288Earlier versions always opened the DATA filehandle in text mode.
2289
2290The glob() operator is implemented via the C<File::Glob> extension,
2291which supports glob syntax of the C shell. This increases the flexibility
2292of the glob() operator, but there may be compatibility issues for
2293programs that relied on the older globbing syntax. If you want to
2294preserve compatibility with the older syntax, you might want to run
2295perl with C<-MFile::DosGlob>. For details and compatibility information,
2296see L<File::Glob>.
2297
2298=head1 Significant bug fixes
2299
2300=head2 <HANDLE> on empty files
2301
2302With C<$/> set to C<undef>, "slurping" an empty file returns a string of
2303zero length (instead of C<undef>, as it used to) the first time the
2304HANDLE is read after C<$/> is set to C<undef>. Further reads yield
2305C<undef>.
2306
2307This means that the following will append "foo" to an empty file (it used
2308to do nothing):
2309
2310 perl -0777 -pi -e 's/^/foo/' empty_file
2311
2312The behaviour of:
2313
2314 perl -pi -e 's/^/foo/' empty_file
2315
2316is unchanged (it continues to leave the file empty).
2317
2318=head2 C<eval '...'> improvements
2319
2320Line numbers (as reflected by caller() and most diagnostics) within
2321C<eval '...'> were often incorrect where here documents were involved.
2322This has been corrected.
2323
2324Lexical lookups for variables appearing in C<eval '...'> within
2325functions that were themselves called within an C<eval '...'> were
2326searching the wrong place for lexicals. The lexical search now
2327correctly ends at the subroutine's block boundary.
2328
2329The use of C<return> within C<eval {...}> caused $@ not to be reset
2330correctly when no exception occurred within the eval. This has
2331been fixed.
2332
2333Parsing of here documents used to be flawed when they appeared as
2334the replacement expression in C<eval 's/.../.../e'>. This has
2335been fixed.
2336
2337=head2 All compilation errors are true errors
2338
2339Some "errors" encountered at compile time were by necessity
2340generated as warnings followed by eventual termination of the
2341program. This enabled more such errors to be reported in a
2342single run, rather than causing a hard stop at the first error
2343that was encountered.
2344
2345The mechanism for reporting such errors has been reimplemented
2346to queue compile-time errors and report them at the end of the
2347compilation as true errors rather than as warnings. This fixes
2348cases where error messages leaked through in the form of warnings
2349when code was compiled at run time using C<eval STRING>, and
2350also allows such errors to be reliably trapped using C<eval "...">.
2351
2352=head2 Implicitly closed filehandles are safer
2353
2354Sometimes implicitly closed filehandles (as when they are localized,
2355and Perl automatically closes them on exiting the scope) could
2356inadvertently set $? or $!. This has been corrected.
2357
2358
2359=head2 Behavior of list slices is more consistent
2360
2361When taking a slice of a literal list (as opposed to a slice of
2362an array or hash), Perl used to return an empty list if the
2363result happened to be composed of all undef values.
2364
2365The new behavior is to produce an empty list if (and only if)
2366the original list was empty. Consider the following example:
2367
2368 @a = (1,undef,undef,2)[2,1,2];
2369
2370The old behavior would have resulted in @a having no elements.
2371The new behavior ensures it has three undefined elements.
2372
2373Note in particular that the behavior of slices of the following
2374cases remains unchanged:
2375
2376 @a = ()[1,2];
2377 @a = (getpwent)[7,0];
2378 @a = (anything_returning_empty_list())[2,1,2];
2379 @a = @b[2,1,2];
2380 @a = @c{'a','b','c'};
2381
2382See L<perldata>.
2383
2384=head2 C<(\$)> prototype and C<$foo{a}>
2385
2386A scalar reference prototype now correctly allows a hash or
2387array element in that slot.
2388
2389=head2 C<goto &sub> and AUTOLOAD
2390
2391The C<goto &sub> construct works correctly when C<&sub> happens
2392to be autoloaded.
2393
2394=head2 C<-bareword> allowed under C<use integer>
2395
2396The autoquoting of barewords preceded by C<-> did not work
2397in prior versions when the C<integer> pragma was enabled.
2398This has been fixed.
2399
2400=head2 Failures in DESTROY()
2401
2402When code in a destructor threw an exception, it went unnoticed
2403in earlier versions of Perl, unless someone happened to be
2404looking in $@ just after the point the destructor happened to
2405run. Such failures are now visible as warnings when warnings are
2406enabled.
2407
2408=head2 Locale bugs fixed
2409
2410printf() and sprintf() previously reset the numeric locale
2411back to the default "C" locale. This has been fixed.
2412
2413Numbers formatted according to the local numeric locale
2414(such as using a decimal comma instead of a decimal dot) caused
2415"isn't numeric" warnings, even while the operations accessing
2416those numbers produced correct results. These warnings have been
2417discontinued.
2418
2419=head2 Memory leaks
2420
2421The C<eval 'return sub {...}'> construct could sometimes leak
2422memory. This has been fixed.
2423
2424Operations that aren't filehandle constructors used to leak memory
2425when used on invalid filehandles. This has been fixed.
2426
2427Constructs that modified C<@_> could fail to deallocate values
2428in C<@_> and thus leak memory. This has been corrected.
2429
2430=head2 Spurious subroutine stubs after failed subroutine calls
2431
2432Perl could sometimes create empty subroutine stubs when a
2433subroutine was not found in the package. Such cases stopped
2434later method lookups from progressing into base packages.
2435This has been corrected.
2436
2437=head2 Taint failures under C<-U>
2438
2439When running in unsafe mode, taint violations could sometimes
2440cause silent failures. This has been fixed.
2441
2442=head2 END blocks and the C<-c> switch
2443
2444Prior versions used to run BEGIN B<and> END blocks when Perl was
2445run in compile-only mode. Since this is typically not the expected
2446behavior, END blocks are not executed anymore when the C<-c> switch
2447is used, or if compilation fails.
2448
2449See L</"Support for CHECK blocks"> for how to run things when the compile
2450phase ends.
2451
2452=head2 Potential to leak DATA filehandles
2453
2454Using the C<__DATA__> token creates an implicit filehandle to
2455the file that contains the token. It is the program's
2456responsibility to close it when it is done reading from it.
2457
2458This caveat is now better explained in the documentation.
2459See L<perldata>.
2460
2461=head1 New or Changed Diagnostics
2462
2463=over 4
2464
2465=item "%s" variable %s masks earlier declaration in same %s
2466
2467(W misc) A "my" or "our" variable has been redeclared in the current scope or statement,
2468effectively eliminating all access to the previous instance. This is almost
2469always a typographical error. Note that the earlier variable will still exist
2470until the end of the scope or until all closure referents to it are
2471destroyed.
2472
2473=item "my sub" not yet implemented
2474
2475(F) Lexically scoped subroutines are not yet implemented. Don't try that
2476yet.
2477
2478=item "our" variable %s redeclared
2479
2480(W misc) You seem to have already declared the same global once before in the
2481current lexical scope.
2482
2483=item '!' allowed only after types %s
2484
2485(F) The '!' is allowed in pack() and unpack() only after certain types.
2486See L<perlfunc/pack>.
2487
2488=item / cannot take a count
2489
2490(F) You had an unpack template indicating a counted-length string,
2491but you have also specified an explicit size for the string.
2492See L<perlfunc/pack>.
2493
2494=item / must be followed by a, A or Z
2495
2496(F) You had an unpack template indicating a counted-length string,
2497which must be followed by one of the letters a, A or Z
2498to indicate what sort of string is to be unpacked.
2499See L<perlfunc/pack>.
2500
2501=item / must be followed by a*, A* or Z*
2502
2503(F) You had a pack template indicating a counted-length string,
2504Currently the only things that can have their length counted are a*, A* or Z*.
2505See L<perlfunc/pack>.
2506
2507=item / must follow a numeric type
2508
2509(F) You had an unpack template that contained a '#',
2510but this did not follow some numeric unpack specification.
2511See L<perlfunc/pack>.
2512
2513=item /%s/: Unrecognized escape \\%c passed through
2514
2515(W regexp) You used a backslash-character combination which is not recognized
2516by Perl. This combination appears in an interpolated variable or a
2517C<'>-delimited regular expression. The character was understood literally.
2518
2519=item /%s/: Unrecognized escape \\%c in character class passed through
2520
2521(W regexp) You used a backslash-character combination which is not recognized
2522by Perl inside character classes. The character was understood literally.
2523
2524=item /%s/ should probably be written as "%s"
2525
2526(W syntax) You have used a pattern where Perl expected to find a string,
2527as in the first argument to C<join>. Perl will treat the true
2528or false result of matching the pattern against $_ as the string,
2529which is probably not what you had in mind.
2530
2531=item %s() called too early to check prototype
2532
2533(W prototype) You've called a function that has a prototype before the parser saw a
2534definition or declaration for it, and Perl could not check that the call
2535conforms to the prototype. You need to either add an early prototype
2536declaration for the subroutine in question, or move the subroutine
2537definition ahead of the call to get proper prototype checking. Alternatively,
2538if you are certain that you're calling the function correctly, you may put
2539an ampersand before the name to avoid the warning. See L<perlsub>.
2540
2541=item %s argument is not a HASH or ARRAY element
2542
2543(F) The argument to exists() must be a hash or array element, such as:
2544
2545 $foo{$bar}
2546 $ref->{"susie"}[12]
2547
2548=item %s argument is not a HASH or ARRAY element or slice
2549
2550(F) The argument to delete() must be either a hash or array element, such as:
2551
2552 $foo{$bar}
2553 $ref->{"susie"}[12]
2554
2555or a hash or array slice, such as:
2556
2557 @foo[$bar, $baz, $xyzzy]
2558 @{$ref->[12]}{"susie", "queue"}
2559
2560=item %s argument is not a subroutine name
2561
2562(F) The argument to exists() for C<exists &sub> must be a subroutine
2563name, and not a subroutine call. C<exists &sub()> will generate this error.
2564
2565=item %s package attribute may clash with future reserved word: %s
2566
2567(W reserved) A lowercase attribute name was used that had a package-specific handler.
2568That name might have a meaning to Perl itself some day, even though it
2569doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
2570See L<attributes>.
2571
2572=item (in cleanup) %s
2573
2574(W misc) This prefix usually indicates that a DESTROY() method raised
2575the indicated exception. Since destructors are usually called by
2576the system at arbitrary points during execution, and often a vast
2577number of times, the warning is issued only once for any number
2578of failures that would otherwise result in the same message being
2579repeated.
2580
2581Failure of user callbacks dispatched using the C<G_KEEPERR> flag
2582could also result in this warning. See L<perlcall/G_KEEPERR>.
2583
2584=item <> should be quotes
2585
2586(F) You wrote C<< require <file> >> when you should have written
2587C<require 'file'>.
2588
2589=item Attempt to join self
2590
2591(F) You tried to join a thread from within itself, which is an
2592impossible task. You may be joining the wrong thread, or you may
2593need to move the join() to some other thread.
2594
2595=item Bad evalled substitution pattern
2596
2597(F) You've used the /e switch to evaluate the replacement for a
2598substitution, but perl found a syntax error in the code to evaluate,
2599most likely an unexpected right brace '}'.
2600
2601=item Bad realloc() ignored
2602
2603(S) An internal routine called realloc() on something that had never been
2604malloc()ed in the first place. Mandatory, but can be disabled by
2605setting environment variable C<PERL_BADFREE> to 1.
2606
2607=item Bareword found in conditional
2608
2609(W bareword) The compiler found a bareword where it expected a conditional,
2610which often indicates that an || or && was parsed as part of the
2611last argument of the previous construct, for example:
2612
2613 open FOO || die;
2614
2615It may also indicate a misspelled constant that has been interpreted
2616as a bareword:
2617
2618 use constant TYPO => 1;
2619 if (TYOP) { print "foo" }
2620
2621The C<strict> pragma is useful in avoiding such errors.
2622
2623=item Binary number > 0b11111111111111111111111111111111 non-portable
2624
2625(W portable) The binary number you specified is larger than 2**32-1
2626(4294967295) and therefore non-portable between systems. See
2627L<perlport> for more on portability concerns.
2628
2629=item Bit vector size > 32 non-portable
2630
2631(W portable) Using bit vector sizes larger than 32 is non-portable.
2632
2633=item Buffer overflow in prime_env_iter: %s
2634
2635(W internal) A warning peculiar to VMS. While Perl was preparing to iterate over
2636%ENV, it encountered a logical name or symbol definition which was too long,
2637so it was truncated to the string shown.
2638
2639=item Can't check filesystem of script "%s"
2640
2641(P) For some reason you can't check the filesystem of the script for nosuid.
2642
2643=item Can't declare class for non-scalar %s in "%s"
2644
2645(S) Currently, only scalar variables can declared with a specific class
2646qualifier in a "my" or "our" declaration. The semantics may be extended
2647for other types of variables in future.
2648
2649=item Can't declare %s in "%s"
2650
2651(F) Only scalar, array, and hash variables may be declared as "my" or
2652"our" variables. They must have ordinary identifiers as names.
2653
2654=item Can't ignore signal CHLD, forcing to default
2655
2656(W signal) Perl has detected that it is being run with the SIGCHLD signal
2657(sometimes known as SIGCLD) disabled. Since disabling this signal
2658will interfere with proper determination of exit status of child
2659processes, Perl has reset the signal to its default value.
2660This situation typically indicates that the parent program under
2661which Perl may be running (e.g., cron) is being very careless.
2662
2663=item Can't modify non-lvalue subroutine call
2664
2665(F) Subroutines meant to be used in lvalue context should be declared as
2666such, see L<perlsub/"Lvalue subroutines">.
2667
2668=item Can't read CRTL environ
2669
2670(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2671from the CRTL's internal environment array and discovered the array was
2672missing. You need to figure out where your CRTL misplaced its environ
2673or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2674
2675=item Can't remove %s: %s, skipping file
2676
2677(S) You requested an inplace edit without creating a backup file. Perl
2678was unable to remove the original file to replace it with the modified
2679file. The file was left unmodified.
2680
2681=item Can't return %s from lvalue subroutine
2682
2683(F) Perl detected an attempt to return illegal lvalues (such
2684as temporary or readonly values) from a subroutine used as an lvalue.
2685This is not allowed.
2686
2687=item Can't weaken a nonreference
2688
2689(F) You attempted to weaken something that was not a reference. Only
2690references can be weakened.
2691
2692=item Character class [:%s:] unknown
2693
2694(F) The class in the character class [: :] syntax is unknown.
2695See L<perlre>.
2696
2697=item Character class syntax [%s] belongs inside character classes
2698
2699(W unsafe) The character class constructs [: :], [= =], and [. .] go
2700I<inside> character classes, the [] are part of the construct,
2701for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2702are not currently implemented; they are simply placeholders for
2703future extensions.
2704
2705=item Constant is not %s reference
2706
2707(F) A constant value (perhaps declared using the C<use constant> pragma)
2708is being dereferenced, but it amounts to the wrong type of reference. The
2709message indicates the type of reference that was expected. This usually
2710indicates a syntax error in dereferencing the constant value.
2711See L<perlsub/"Constant Functions"> and L<constant>.
2712
2713=item constant(%s): %s
2714
2715(F) The parser found inconsistencies either while attempting to define an
2716overloaded constant, or when trying to find the character name specified
2717in the C<\N{...}> escape. Perhaps you forgot to load the corresponding
2718C<overload> or C<charnames> pragma? See L<charnames> and L<overload>.
2719
2720=item CORE::%s is not a keyword
2721
2722(F) The CORE:: namespace is reserved for Perl keywords.
2723
2724=item defined(@array) is deprecated
2725
2726(D) defined() is not usually useful on arrays because it checks for an
2727undefined I<scalar> value. If you want to see if the array is empty,
2728just use C<if (@array) { # not empty }> for example.
2729
2730=item defined(%hash) is deprecated
2731
2732(D) defined() is not usually useful on hashes because it checks for an
2733undefined I<scalar> value. If you want to see if the hash is empty,
2734just use C<if (%hash) { # not empty }> for example.
2735
2736=item Did not produce a valid header
2737
2738See Server error.
2739
2740=item (Did you mean "local" instead of "our"?)
2741
2742(W misc) Remember that "our" does not localize the declared global variable.
2743You have declared it again in the same lexical scope, which seems superfluous.
2744
2745=item Document contains no data
2746
2747See Server error.
2748
2749=item entering effective %s failed
2750
2751(F) While under the C<use filetest> pragma, switching the real and
2752effective uids or gids failed.
2753
2754=item false [] range "%s" in regexp
2755
2756(W regexp) A character class range must start and end at a literal character, not
2757another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2758range is interpreted as a literal "-". Consider quoting the "-", "\-".
2759See L<perlre>.
2760
2761=item Filehandle %s opened only for output
2762
2763(W io) You tried to read from a filehandle opened only for writing. If you
2764intended it to be a read/write filehandle, you needed to open it with
2765"+<" or "+>" or "+>>" instead of with "<" or nothing. If
2766you intended only to read from the file, use "<". See
2767L<perlfunc/open>.
2768
2769=item flock() on closed filehandle %s
2770
2771(W closed) The filehandle you're attempting to flock() got itself closed some
2772time before now. Check your logic flow. flock() operates on filehandles.
2773Are you attempting to call flock() on a dirhandle by the same name?
2774
2775=item Global symbol "%s" requires explicit package name
2776
2777(F) You've said "use strict vars", which indicates that all variables
2778must either be lexically scoped (using "my"), declared beforehand using
2779"our", or explicitly qualified to say which package the global variable
2780is in (using "::").
2781
2782=item Hexadecimal number > 0xffffffff non-portable
2783
2784(W portable) The hexadecimal number you specified is larger than 2**32-1
2785(4294967295) and therefore non-portable between systems. See
2786L<perlport> for more on portability concerns.
2787
2788=item Ill-formed CRTL environ value "%s"
2789
2790(W internal) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2791environ array, and encountered an element without the C<=> delimiter
2792used to separate keys from values. The element is ignored.
2793
2794=item Ill-formed message in prime_env_iter: |%s|
2795
2796(W internal) A warning peculiar to VMS. Perl tried to read a logical name
2797or CLI symbol definition when preparing to iterate over %ENV, and
2798didn't see the expected delimiter between key and value, so the
2799line was ignored.
2800
2801=item Illegal binary digit %s
2802
2803(F) You used a digit other than 0 or 1 in a binary number.
2804
2805=item Illegal binary digit %s ignored
2806
2807(W digit) You may have tried to use a digit other than 0 or 1 in a binary number.
2808Interpretation of the binary number stopped before the offending digit.
2809
2810=item Illegal number of bits in vec
2811
2812(F) The number of bits in vec() (the third argument) must be a power of
2813two from 1 to 32 (or 64, if your platform supports that).
2814
2815=item Integer overflow in %s number
2816
2817(W overflow) The hexadecimal, octal or binary number you have specified either
2818as a literal or as an argument to hex() or oct() is too big for your
2819architecture, and has been converted to a floating point number. On a
282032-bit architecture the largest hexadecimal, octal or binary number
2821representable without overflow is 0xFFFFFFFF, 037777777777, or
28220b11111111111111111111111111111111 respectively. Note that Perl
2823transparently promotes all numbers to a floating point representation
2824internally--subject to loss of precision errors in subsequent
2825operations.
2826
2827=item Invalid %s attribute: %s
2828
2829The indicated attribute for a subroutine or variable was not recognized
2830by Perl or by a user-supplied handler. See L<attributes>.
2831
2832=item Invalid %s attributes: %s
2833
2834The indicated attributes for a subroutine or variable were not recognized
2835by Perl or by a user-supplied handler. See L<attributes>.
2836
2837=item invalid [] range "%s" in regexp
2838
2839The offending range is now explicitly displayed.
2840
2841=item Invalid separator character %s in attribute list
2842
2843(F) Something other than a colon or whitespace was seen between the
2844elements of an attribute list. If the previous attribute
2845had a parenthesised parameter list, perhaps that list was terminated
2846too soon. See L<attributes>.
2847
2848=item Invalid separator character %s in subroutine attribute list
2849
2850(F) Something other than a colon or whitespace was seen between the
2851elements of a subroutine attribute list. If the previous attribute
2852had a parenthesised parameter list, perhaps that list was terminated
2853too soon.
2854
2855=item leaving effective %s failed
2856
2857(F) While under the C<use filetest> pragma, switching the real and
2858effective uids or gids failed.
2859
2860=item Lvalue subs returning %s not implemented yet
2861
2862(F) Due to limitations in the current implementation, array and hash
2863values cannot be returned in subroutines used in lvalue context.
2864See L<perlsub/"Lvalue subroutines">.
2865
2866=item Method %s not permitted
2867
2868See Server error.
2869
2870=item Missing %sbrace%s on \N{}
2871
2872(F) Wrong syntax of character name literal C<\N{charname}> within
2873double-quotish context.
2874
2875=item Missing command in piped open
2876
2877(W pipe) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2878construction, but the command was missing or blank.
2879
2880=item Missing name in "my sub"
2881
2882(F) The reserved syntax for lexically scoped subroutines requires that they
2883have a name with which they can be found.
2884
2885=item No %s specified for -%c
2886
2887(F) The indicated command line switch needs a mandatory argument, but
2888you haven't specified one.
2889
2890=item No package name allowed for variable %s in "our"
2891
2892(F) Fully qualified variable names are not allowed in "our" declarations,
2893because that doesn't make much sense under existing semantics. Such
2894syntax is reserved for future extensions.
2895
2896=item No space allowed after -%c
2897
2898(F) The argument to the indicated command line switch must follow immediately
2899after the switch, without intervening spaces.
2900
2901=item no UTC offset information; assuming local time is UTC
2902
2903(S) A warning peculiar to VMS. Perl was unable to find the local
2904timezone offset, so it's assuming that local system time is equivalent
2905to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2906to translate to the number of seconds which need to be added to UTC to
2907get local time.
2908
2909=item Octal number > 037777777777 non-portable
2910
2911(W portable) The octal number you specified is larger than 2**32-1 (4294967295)
2912and therefore non-portable between systems. See L<perlport> for more
2913on portability concerns.
2914
2915See also L<perlport> for writing portable code.
2916
2917=item panic: del_backref
2918
2919(P) Failed an internal consistency check while trying to reset a weak
2920reference.
2921
2922=item panic: kid popen errno read
2923
2924(F) forked child returned an incomprehensible message about its errno.
2925
2926=item panic: magic_killbackrefs
2927
2928(P) Failed an internal consistency check while trying to reset all weak
2929references to an object.
2930
2931=item Parentheses missing around "%s" list
2932
2933(W parenthesis) You said something like
2934
2935 my $foo, $bar = @_;
2936
2937when you meant
2938
2939 my ($foo, $bar) = @_;
2940
2941Remember that "my", "our", and "local" bind tighter than comma.
2942
2943=item Possible unintended interpolation of %s in string
2944
2945(W ambiguous) It used to be that Perl would try to guess whether you
2946wanted an array interpolated or a literal @. It no longer does this;
2947arrays are now I<always> interpolated into strings. This means that
2948if you try something like:
2949
2950 print "fred@example.com";
2951
2952and the array C<@example> doesn't exist, Perl is going to print
2953C<fred.com>, which is probably not what you wanted. To get a literal
2954C<@> sign in a string, put a backslash before it, just as you would
2955to get a literal C<$> sign.
2956
2957=item Possible Y2K bug: %s
2958
2959(W y2k) You are concatenating the number 19 with another number, which
2960could be a potential Year 2000 problem.
2961
2962=item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
2963
2964(W deprecated) You have written something like this:
2965
2966 sub doit
2967 {
2968 use attrs qw(locked);
2969 }
2970
2971You should use the new declaration syntax instead.
2972
2973 sub doit : locked
2974 {
2975 ...
2976
2977The C<use attrs> pragma is now obsolete, and is only provided for
2978backward-compatibility. See L<perlsub/"Subroutine Attributes">.
2979
493a87da
JH
2980=item Premature end of script headers
2981
2982See Server error.
2983
2984=item Repeat count in pack overflows
2985
2986(F) You can't specify a repeat count so large that it overflows
2987your signed integers. See L<perlfunc/pack>.
2988
2989=item Repeat count in unpack overflows
2990
2991(F) You can't specify a repeat count so large that it overflows
2992your signed integers. See L<perlfunc/unpack>.
2993
2994=item realloc() of freed memory ignored
2995
2996(S) An internal routine called realloc() on something that had already
2997been freed.
2998
2999=item Reference is already weak
3000
3001(W misc) You have attempted to weaken a reference that is already weak.
3002Doing so has no effect.
3003
3004=item setpgrp can't take arguments
3005
3006(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
3007unlike POSIX setpgid(), which takes a process ID and process group ID.
3008
3009=item Strange *+?{} on zero-length expression
3010
3011(W regexp) You applied a regular expression quantifier in a place where it
3012makes no sense, such as on a zero-width assertion.
3013Try putting the quantifier inside the assertion instead. For example,
3014the way to match "abc" provided that it is followed by three
3015repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
3016
3017=item switching effective %s is not implemented
3018
3019(F) While under the C<use filetest> pragma, we cannot switch the
3020real and effective uids or gids.
3021
3022=item This Perl can't reset CRTL environ elements (%s)
3023
3024=item This Perl can't set CRTL environ elements (%s=%s)
3025
3026(W internal) Warnings peculiar to VMS. You tried to change or delete an element
3027of the CRTL's internal environ array, but your copy of Perl wasn't
3028built with a CRTL that contained the setenv() function. You'll need to
3029rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
3030L<perlvms>) so that the environ array isn't the target of the change to
3031%ENV which produced the warning.
3032
3033=item Too late to run %s block
3034
3035(W void) A CHECK or INIT block is being defined during run time proper,
3036when the opportunity to run them has already passed. Perhaps you are
3037loading a file with C<require> or C<do> when you should be using
3038C<use> instead. Or perhaps you should put the C<require> or C<do>
3039inside a BEGIN block.
3040
3041=item Unknown open() mode '%s'
3042
3043(F) The second argument of 3-argument open() is not among the list
3044of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
3045C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
3046
3047=item Unknown process %x sent message to prime_env_iter: %s
3048
3049(P) An error peculiar to VMS. Perl was reading values for %ENV before
3050iterating over it, and someone else stuck a message in the stream of
3051data Perl expected. Someone's very confused, or perhaps trying to
3052subvert Perl's population of %ENV for nefarious purposes.
3053
3054=item Unrecognized escape \\%c passed through
3055
3056(W misc) You used a backslash-character combination which is not recognized
3057by Perl. The character was understood literally.
3058
3059=item Unterminated attribute parameter in attribute list
3060
3061(F) The lexer saw an opening (left) parenthesis character while parsing an
3062attribute list, but the matching closing (right) parenthesis
3063character was not found. You may need to add (or remove) a backslash
3064character to get your parentheses to balance. See L<attributes>.
3065
3066=item Unterminated attribute list
3067
3068(F) The lexer found something other than a simple identifier at the start
3069of an attribute, and it wasn't a semicolon or the start of a
3070block. Perhaps you terminated the parameter list of the previous attribute
3071too soon. See L<attributes>.
3072
3073=item Unterminated attribute parameter in subroutine attribute list
3074
3075(F) The lexer saw an opening (left) parenthesis character while parsing a
3076subroutine attribute list, but the matching closing (right) parenthesis
3077character was not found. You may need to add (or remove) a backslash
3078character to get your parentheses to balance.
3079
3080=item Unterminated subroutine attribute list
3081
3082(F) The lexer found something other than a simple identifier at the start
3083of a subroutine attribute, and it wasn't a semicolon or the start of a
3084block. Perhaps you terminated the parameter list of the previous attribute
3085too soon.
3086
3087=item Value of CLI symbol "%s" too long
3088
3089(W misc) A warning peculiar to VMS. Perl tried to read the value of an %ENV
3090element from a CLI symbol table, and found a resultant string longer
3091than 1024 characters. The return value has been truncated to 1024
3092characters.
3093
3094=item Version number must be a constant number
3095
3096(P) The attempt to translate a C<use Module n.n LIST> statement into
3097its equivalent C<BEGIN> block found an internal inconsistency with
3098the version number.
3099
3100=back
3101
3102=head1 New tests
3103
3104=over 4
3105
3106=item lib/attrs
3107
3108Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
3109
3110=item lib/env
3111
3112Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
3113
3114=item lib/env-array
3115
3116Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
3117
3118=item lib/io_const
3119
3120IO constants (SEEK_*, _IO*).
3121
3122=item lib/io_dir
3123
3124Directory-related IO methods (new, read, close, rewind, tied delete).
3125
3126=item lib/io_multihomed
3127
3128INET sockets with multi-homed hosts.
3129
3130=item lib/io_poll
3131
3132IO poll().
3133
3134=item lib/io_unix
3135
3136UNIX sockets.
3137
3138=item op/attrs
3139
3140Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
3141
3142=item op/filetest
3143
3144File test operators.
3145
3146=item op/lex_assign
3147
3148Verify operations that access pad objects (lexicals and temporaries).
3149
3150=item op/exists_sub
3151
3152Verify C<exists &sub> operations.
3153
3154=back
3155
3156=head1 Incompatible Changes
3157
3158=head2 Perl Source Incompatibilities
3159
3160Beware that any new warnings that have been added or old ones
3161that have been enhanced are B<not> considered incompatible changes.
3162
3163Since all new warnings must be explicitly requested via the C<-w>
3164switch or the C<warnings> pragma, it is ultimately the programmer's
3165responsibility to ensure that warnings are enabled judiciously.
3166
3167=over 4
3168
3169=item CHECK is a new keyword
3170
3171All subroutine definitions named CHECK are now special. See
3172C</"Support for CHECK blocks"> for more information.
3173
3174=item Treatment of list slices of undef has changed
3175
3176There is a potential incompatibility in the behavior of list slices
3177that are comprised entirely of undefined values.
3178See L</"Behavior of list slices is more consistent">.
3179
3180=item Format of $English::PERL_VERSION is different
3181
3182The English module now sets $PERL_VERSION to $^V (a string value) rather
3183than C<$]> (a numeric value). This is a potential incompatibility.
3184Send us a report via perlbug if you are affected by this.
3185
3186See L</"Improved Perl version numbering system"> for the reasons for
3187this change.
3188
3189=item Literals of the form C<1.2.3> parse differently
3190
3191Previously, numeric literals with more than one dot in them were
3192interpreted as a floating point number concatenated with one or more
3193numbers. Such "numbers" are now parsed as strings composed of the
3194specified ordinals.
3195
3196For example, C<print 97.98.99> used to output C<97.9899> in earlier
3197versions, but now prints C<abc>.
3198
3199See L</"Support for strings represented as a vector of ordinals">.
3200
3201=item Possibly changed pseudo-random number generator
3202
3203Perl programs that depend on reproducing a specific set of pseudo-random
3204numbers may now produce different output due to improvements made to the
3205rand() builtin. You can use C<sh Configure -Drandfunc=rand> to obtain
3206the old behavior.
3207
3208See L</"Better pseudo-random number generator">.
3209
3210=item Hashing function for hash keys has changed
3211
3212Even though Perl hashes are not order preserving, the apparently
3213random order encountered when iterating on the contents of a hash
3214is actually determined by the hashing algorithm used. Improvements
3215in the algorithm may yield a random order that is B<different> from
3216that of previous versions, especially when iterating on hashes.
3217
3218See L</"Better worst-case behavior of hashes"> for additional
3219information.
3220
3221=item C<undef> fails on read only values
3222
3223Using the C<undef> operator on a readonly value (such as $1) has
3224the same effect as assigning C<undef> to the readonly value--it
3225throws an exception.
3226
3227=item Close-on-exec bit may be set on pipe and socket handles
3228
3229Pipe and socket handles are also now subject to the close-on-exec
3230behavior determined by the special variable $^F.
3231
3232See L</"More consistent close-on-exec behavior">.
3233
3234=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
3235
3236Perl 5.004 deprecated the interpretation of C<$$1> and
3237similar within interpolated strings to mean C<$$ . "1">,
3238but still allowed it.
3239
3240In Perl 5.6.0 and later, C<"$$1"> always means C<"${$1}">.
3241
3242=item delete(), each(), values() and C<\(%h)>
3243
3244operate on aliases to values, not copies
3245
3246delete(), each(), values() and hashes (e.g. C<\(%h)>)
3247in a list context return the actual
3248values in the hash, instead of copies (as they used to in earlier
3249versions). Typical idioms for using these constructs copy the
3250returned values, but this can make a significant difference when
3251creating references to the returned values. Keys in the hash are still
3252returned as copies when iterating on a hash.
3253
3254See also L</"delete(), each(), values() and hash iteration are faster">.
3255
3256=item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
3257
3258vec() generates a run-time error if the BITS argument is not
3259a valid power-of-two integer.
3260
3261=item Text of some diagnostic output has changed
3262
3263Most references to internal Perl operations in diagnostics
3264have been changed to be more descriptive. This may be an
3265issue for programs that may incorrectly rely on the exact
3266text of diagnostics for proper functioning.
3267
3268=item C<%@> has been removed
3269
3270The undocumented special variable C<%@> that used to accumulate
3271"background" errors (such as those that happen in DESTROY())
3272has been removed, because it could potentially result in memory
3273leaks.
3274
3275=item Parenthesized not() behaves like a list operator
3276
3277The C<not> operator now falls under the "if it looks like a function,
3278it behaves like a function" rule.
3279
3280As a result, the parenthesized form can be used with C<grep> and C<map>.
3281The following construct used to be a syntax error before, but it works
3282as expected now:
3283
3284 grep not($_), @things;
3285
3286On the other hand, using C<not> with a literal list slice may not
3287work. The following previously allowed construct:
3288
3289 print not (1,2,3)[0];
3290
3291needs to be written with additional parentheses now:
3292
3293 print not((1,2,3)[0]);
3294
3295The behavior remains unaffected when C<not> is not followed by parentheses.
3296
3297=item Semantics of bareword prototype C<(*)> have changed
3298
3299The semantics of the bareword prototype C<*> have changed. Perl 5.005
3300always coerced simple scalar arguments to a typeglob, which wasn't useful
3301in situations where the subroutine must distinguish between a simple
3302scalar and a typeglob. The new behavior is to not coerce bareword
3303arguments to a typeglob. The value will always be visible as either
3304a simple scalar or as a reference to a typeglob.
3305
3306See L</"More functional bareword prototype (*)">.
3307
3308=item Semantics of bit operators may have changed on 64-bit platforms
3309
3310If your platform is either natively 64-bit or if Perl has been
3311configured to used 64-bit integers, i.e., $Config{ivsize} is 8,
3312there may be a potential incompatibility in the behavior of bitwise
3313numeric operators (& | ^ ~ << >>). These operators used to strictly
3314operate on the lower 32 bits of integers in previous versions, but now
3315operate over the entire native integral width. In particular, note
3316that unary C<~> will produce different results on platforms that have
3317different $Config{ivsize}. For portability, be sure to mask off
3318the excess bits in the result of unary C<~>, e.g., C<~$x & 0xffffffff>.
3319
3320See L</"Bit operators support full native integer width">.
3321
3322=item More builtins taint their results
3323
3324As described in L</"Improved security features">, there may be more
3325sources of taint in a Perl program.
3326
3327To avoid these new tainting behaviors, you can build Perl with the
3328Configure option C<-Accflags=-DINCOMPLETE_TAINTS>. Beware that the
3329ensuing perl binary may be insecure.
3330
3331=back
3332
3333=head2 C Source Incompatibilities
3334
3335=over 4
3336
3337=item C<PERL_POLLUTE>
3338
3339Release 5.005 grandfathered old global symbol names by providing preprocessor
3340macros for extension source compatibility. As of release 5.6.0, these
3341preprocessor definitions are not available by default. You need to explicitly
3342compile perl with C<-DPERL_POLLUTE> to get these definitions. For
3343extensions still using the old symbols, this option can be
3344specified via MakeMaker:
3345
3346 perl Makefile.PL POLLUTE=1
3347
3348=item C<PERL_IMPLICIT_CONTEXT>
3349
3350This new build option provides a set of macros for all API functions
3351such that an implicit interpreter/thread context argument is passed to
3352every API function. As a result of this, something like C<sv_setsv(foo,bar)>
3353amounts to a macro invocation that actually translates to something like
3354C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
3355to not have any significant source compatibility issues, the difference
3356between a macro and a real function call will need to be considered.
3357
3358This means that there B<is> a source compatibility issue as a result of
3359this if your extensions attempt to use pointers to any of the Perl API
3360functions.
3361
3362Note that the above issue is not relevant to the default build of
3363Perl, whose interfaces continue to match those of prior versions
3364(but subject to the other options described here).
3365
27f68d5f
KW
3366See L<perlguts/Background and PERL_IMPLICIT_CONTEXT> for detailed information
3367on the ramifications of building Perl with this option.
493a87da
JH
3368
3369 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
3370 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
3371 intended to be enabled by users at this time.
3372
3373=item C<PERL_POLLUTE_MALLOC>
3374
3375Enabling Perl's malloc in release 5.005 and earlier caused the namespace of
3376the system's malloc family of functions to be usurped by the Perl versions,
3377since by default they used the same names. Besides causing problems on
3378platforms that do not allow these functions to be cleanly replaced, this
3379also meant that the system versions could not be called in programs that
3380used Perl's malloc. Previous versions of Perl have allowed this behaviour
3381to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
3382definitions.
3383
3384As of release 5.6.0, Perl's malloc family of functions have default names
3385distinct from the system versions. You need to explicitly compile perl with
3386C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
3387and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
3388the default.
3389
3390Note that these functions do B<not> constitute Perl's memory allocation API.
3391See L<perlguts/"Memory Allocation"> for further information about that.
3392
3393=back
3394
3395=head2 Compatible C Source API Changes
3396
3397=over 4
3398
3399=item C<PATCHLEVEL> is now C<PERL_VERSION>
3400
3401The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
3402are now available by default from perl.h, and reflect the base revision,
3403patchlevel, and subversion respectively. C<PERL_REVISION> had no
3404prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
3405previously available as C<PATCHLEVEL> and C<SUBVERSION>.
3406
3407The new names cause less pollution of the B<cpp> namespace and reflect what
3408the numbers have come to stand for in common practice. For compatibility,
3409the old names are still supported when F<patchlevel.h> is explicitly
3410included (as required before), so there is no source incompatibility
3411from the change.
3412
3413=back
3414
3415=head2 Binary Incompatibilities
3416
3417In general, the default build of this release is expected to be binary
3418compatible for extensions built with the 5.005 release or its maintenance
3419versions. However, specific platforms may have broken binary compatibility
3420due to changes in the defaults used in hints files. Therefore, please be
3421sure to always check the platform-specific README files for any notes to
3422the contrary.
3423
3424The usethreads or usemultiplicity builds are B<not> binary compatible
3425with the corresponding builds in 5.005.
3426
3427On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
3428among others), purely internal symbols such as parser functions and the
3429run time opcodes are not exported by default. Perl 5.005 used to export
3430all functions irrespective of whether they were considered part of the
3431public API or not.
3432
3433For the full list of public API functions, see L<perlapi>.
3434
3435=head1 Known Problems
3436
3437=head2 Localizing a tied hash element may leak memory
3438
3439As of the 5.6.1 release, there is a known leak when code such as this
3440is executed:
3441
3442 use Tie::Hash;
3443 tie my %tie_hash => 'Tie::StdHash';
3444
3445 ...
3446
3447 local($tie_hash{Foo}) = 1; # leaks
3448
3449=head2 Known test failures
3450
3451=over
3452
818c4caa 3453=item *
5cb3728c
RB
3454
345564-bit builds
493a87da
JH
3456
3457Subtest #15 of lib/b.t may fail under 64-bit builds on platforms such
3458as HP-UX PA64 and Linux IA64. The issue is still being investigated.
3459
3460The lib/io_multihomed test may hang in HP-UX if Perl has been
3461configured to be 64-bit. Because other 64-bit platforms do not
3462hang in this test, HP-UX is suspect. All other tests pass
3463in 64-bit HP-UX. The test attempts to create and connect to
3464"multihomed" sockets (sockets which have multiple IP addresses).
3465
3466Note that 64-bit support is still experimental.
3467
818c4caa 3468=item *
5cb3728c
RB
3469
3470Failure of Thread tests
493a87da
JH
3471
3472The subtests 19 and 20 of lib/thr5005.t test are known to fail due to
3473fundamental problems in the 5.005 threading implementation. These are
3474not new failures--Perl 5.005_0x has the same bugs, but didn't have these
3475tests. (Note that support for 5.005-style threading remains experimental.)
3476
818c4caa 3477=item *
5cb3728c
RB
3478
3479NEXTSTEP 3.3 POSIX test failure
493a87da
JH
3480
3481In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the
3482operating system libraries is buggy: the %j format numbers the days of
3483a month starting from zero, which, while being logical to programmers,
3484will cause the subtests 19 to 27 of the lib/posix test may fail.
3485
818c4caa 3486=item *
5cb3728c
RB
3487
3488Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc
493a87da
JH
3489
3490If compiled with gcc 2.95 the lib/sdbm test will fail (dump core).
3491The cure is to use the vendor cc, it comes with the operating system
3492and produces good code.
3493
3494=back
3495
3496=head2 EBCDIC platforms not fully supported
3497
3498In earlier releases of Perl, EBCDIC environments like OS390 (also
3499known as Open Edition MVS) and VM-ESA were supported. Due to changes
3500required by the UTF-8 (Unicode) support, the EBCDIC platforms are not
3501supported in Perl 5.6.0.
3502
3503The 5.6.1 release improves support for EBCDIC platforms, but they
3504are not fully supported yet.
3505
3506=head2 UNICOS/mk CC failures during Configure run
3507
3508In UNICOS/mk the following errors may appear during the Configure run:
3509
3510 Guessing which symbols your C compiler and preprocessor define...
3511 CC-20 cc: ERROR File = try.c, Line = 3
3512 ...
3513 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
3514 ...
3515 4 errors detected in the compilation of "try.c".
3516
3517The culprit is the broken awk of UNICOS/mk. The effect is fortunately
3518rather mild: Perl itself is not adversely affected by the error, only
3519the h2ph utility coming with Perl, and that is rather rarely needed
3520these days.
3521
3522=head2 Arrow operator and arrays
3523
3524When the left argument to the arrow operator C<< -> >> is an array, or
3525the C<scalar> operator operating on an array, the result of the
3526operation must be considered erroneous. For example:
3527
3528 @x->[2]
3529 scalar(@x)->[2]
3530
3531These expressions will get run-time errors in some future release of
3532Perl.
3533
3534=head2 Experimental features
3535
3536As discussed above, many features are still experimental. Interfaces and
3537implementation of these features are subject to change, and in extreme cases,
3538even subject to removal in some future release of Perl. These features
3539include the following:
3540
3541=over 4
3542
3543=item Threads
3544
3545=item Unicode
3546
3547=item 64-bit support
3548
3549=item Lvalue subroutines
3550
3551=item Weak references
3552
3553=item The pseudo-hash data type
3554
3555=item The Compiler suite
3556
3557=item Internal implementation of file globbing
3558
3559=item The DB module
3560
3561=item The regular expression code constructs:
3562
3563C<(?{ code })> and C<(??{ code })>
3564
3565=back
3566
3567=head1 Obsolete Diagnostics
3568
3569=over 4
3570
3571=item Character class syntax [: :] is reserved for future extensions
3572
3573(W) Within regular expression character classes ([]) the syntax beginning
3574with "[:" and ending with ":]" is reserved for future extensions.
3575If you need to represent those character sequences inside a regular
3576expression character class, just quote the square brackets with the
3577backslash: "\[:" and ":\]".
3578
3579=item Ill-formed logical name |%s| in prime_env_iter
3580
3581(W) A warning peculiar to VMS. A logical name was encountered when preparing
3582to iterate over %ENV which violates the syntactic rules governing logical
3583names. Because it cannot be translated normally, it is skipped, and will not
3584appear in %ENV. This may be a benign occurrence, as some software packages
3585might directly modify logical name tables and introduce nonstandard names,
3586or it may indicate that a logical name table has been corrupted.
3587
3588=item In string, @%s now must be written as \@%s
3589
3590The description of this error used to say:
3591
3592 (Someday it will simply assume that an unbackslashed @
3593 interpolates an array.)
3594
3595That day has come, and this fatal error has been removed. It has been
3596replaced by a non-fatal warning instead.
3597See L</Arrays now always interpolate into double-quoted strings> for
3598details.
3599
3600=item Probable precedence problem on %s
3601
3602(W) The compiler found a bareword where it expected a conditional,
3603which often indicates that an || or && was parsed as part of the
3604last argument of the previous construct, for example:
3605
3606 open FOO || die;
3607
3608=item regexp too big
3609
3610(F) The current implementation of regular expressions uses shorts as
3611address offsets within a string. Unfortunately this means that if
3612the regular expression compiles to longer than 32767, it'll blow up.
3613Usually when you want a regular expression this big, there is a better
3614way to do it with multiple statements. See L<perlre>.
3615
3616=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
3617
3618(D) Perl versions before 5.004 misinterpreted any type marker followed
3619by "$" and a digit. For example, "$$0" was incorrectly taken to mean
3620"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
3621
3622However, the developers of Perl 5.004 could not fix this bug completely,
3623because at least two widely-used modules depend on the old meaning of
3624"$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
3625old (broken) way inside strings; but it generates this message as a
3626warning. And in Perl 5.005, this special treatment will cease.
3627
3628=back
3629
3630=head1 Reporting Bugs
3631
3632If you find what you think is a bug, you might check the
3633articles recently posted to the comp.lang.perl.misc newsgroup.
f224927c 3634There may also be information at http://www.perl.com/ , the Perl
493a87da
JH
3635Home Page.
3636
3637If you believe you have an unreported bug, please run the B<perlbug>
3638program included with your release. Be sure to trim your bug down
3639to a tiny but sufficient test case. Your bug report, along with the
3640output of C<perl -V>, will be sent off to perlbug@perl.org to be
3641analysed by the Perl porting team.
3642
3643=head1 SEE ALSO
3644
3645The F<Changes> file for exhaustive details on what changed.
3646
3647The F<INSTALL> file for how to build Perl.
3648
3649The F<README> file for general stuff.
3650
3651The F<Artistic> and F<Copying> files for copyright information.
3652
3653=head1 HISTORY
3654
3655Written by Gurusamy Sarathy <F<gsar@ActiveState.com>>, with many
3656contributions from The Perl Porters.
3657
3658Send omissions or corrections to <F<perlbug@perl.org>>.
3659
3660=cut