5 [ this is a template for a new perldelta file. Any text flagged as XXX needs
6 to be processed before release. ]
8 perldelta - what is new for perl v5.21.4
12 This document describes differences between the 5.21.3 release and the 5.21.4
15 If you are upgrading from an earlier release such as 5.21.2, first read
16 L<perl5213delta>, which describes differences between 5.21.2 and 5.21.3.
20 XXX Any important notices here
22 =head1 Core Enhancements
24 XXX New core language features go here. Summarize user-visible core language
25 enhancements. Particularly prominent performance optimisations could go
26 here, but most should go in the L</Performance Enhancements> section.
28 [ List each enhancement as a =head2 entry ]
32 XXX Any security-related notices go here. In particular, any security
33 vulnerabilities closed should be noted here rather than in the
34 L</Selected Bug Fixes> section.
36 [ List each security issue as a =head2 entry ]
38 =head1 Incompatible Changes
40 XXX For a release on a stable branch, this section aspires to be:
42 There are no changes intentionally incompatible with 5.XXX.XXX
43 If any exist, they are bugs, and we request that you submit a
44 report. See L</Reporting Bugs> below.
46 [ List each incompatible change as a =head2 entry ]
50 XXX Any deprecated features, syntax, modules etc. should be listed here.
52 =head2 Module removals
54 XXX Remove this section if inapplicable.
56 The following modules will be removed from the core distribution in a
57 future release, and will at that time need to be installed from CPAN.
58 Distributions on CPAN which require these modules will need to list them as
61 The core versions of these modules will now issue C<"deprecated">-category
62 warnings to alert you to this fact. To silence these deprecation warnings,
63 install the modules in question from CPAN.
65 Note that these are (with rare exceptions) fine modules that you are encouraged
66 to continue to use. Their disinclusion from core primarily hinges on their
67 necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
68 not usually on concerns over their design.
74 XXX Note that deprecated modules should be listed here even if they are listed
75 as an updated module in the L</Modules and Pragmata> section.
79 [ List each other deprecation as a =head2 entry ]
81 =head1 Performance Enhancements
83 XXX Changes which enhance performance without changing behaviour go here.
84 There may well be none in a stable release.
86 [ List each enhancement as a =item entry ]
96 =head1 Modules and Pragmata
98 XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
99 go here. If Module::CoreList is updated, generate an initial draft of the
100 following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
101 for important changes should then be added by hand. In an ideal world,
102 dual-life modules would have a F<Changes> file that could be cribbed.
104 [ Within each section, list entries as a =item entry ]
106 =head2 New Modules and Pragmata
116 =head2 Updated Modules and Pragmata
122 L<XXX> has been upgraded from version A.xx to B.yy.
126 L<File::Find> has been upgraded from version 1.27 to 1.28.
128 C<find()> and C<finddepth()> will now warn if passed inappropriate or
133 L<B::Concise> has been upgraded from version 0.992 to 0.993.
138 L<ExtUtils::CBuilder> has been upgraded from version 0.280216 to 0.280219.
143 L<ExtUtils::Manifest> has been upgraded from version 1.65 to 1.66.
148 L<HTTP::Tiny> has been upgraded from version 0.047 to 0.048.
152 L<Module::CoreList> has been upgraded from version 5.021003 to 5.021004.
156 L<POSIX> has been upgraded from version 1.42 to 1.43.
160 L<Pod::Perldoc> has been upgraded from version 3.23 to 3.24.
164 L<constant> has been upgraded from version 1.31 to 1.32.
166 It now accepts fully-qualified constant names, allowing constants to be
167 defined in packages other than the caller.
171 L<threads> has been upgraded from version 1.95 to 1.96.
175 =head2 Removed Modules and Pragmata
187 XXX Changes to files in F<pod/> go here. Consider grouping entries by
188 file and be sure to link to the appropriate page, e.g. L<perlfunc>.
190 =head2 New Documentation
192 XXX Changes which create B<new> files in F<pod/> go here.
196 XXX Description of the purpose of the new file here
198 =head2 Changes to Existing Documentation
200 XXX Changes which significantly change existing files in F<pod/> go here.
201 However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
210 XXX Description of the change here
216 The following additions or changes have been made to diagnostic output,
217 including warnings and fatal error messages. For the complete list of
218 diagnostic messages, see L<perldiag>.
220 XXX New or changed warnings emitted by the core's C<C> code go here. Also
221 include any changes in L<perldiag> that reconcile it to the C<C> code.
223 =head2 New Diagnostics
225 XXX Newly added diagnostic messages go under here, separated into New Errors
234 XXX L<message|perldiag/"message">
244 XXX L<message|perldiag/"message">
248 =head2 Changes to Existing Diagnostics
250 XXX Changes (i.e. rewording) of diagnostic messages go here
256 XXX Describe change here
260 =head1 Utility Changes
262 XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
263 Most of these are built within the directory F<utils>.
265 [ List utility changes as a =head2 entry for each utility and =item
266 entries for each change
267 Use L<XXX> with program names to get proper documentation linking. ]
279 =head1 Configuration and Compilation
281 XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
282 go here. Any other changes to the Perl build process should be listed here.
283 However, any platform-specific changes should be listed in the
284 L</Platform Support> section, instead.
286 [ List changes as a =item entry ].
298 XXX Any significant changes to the testing of a freshly built perl should be
299 listed here. Changes which create B<new> files in F<t/> go here as do any
300 large changes to the testing harness (e.g. when parallel testing was added).
301 Changes to existing files in F<t/> aren't worth summarizing, although the bugs
302 that they represent may be covered elsewhere.
304 [ List each test improvement as a =item entry ]
314 =head1 Platform Support
316 XXX Any changes to platform support should be listed in the sections below.
318 [ Within the sections, list each platform as a =item entry with specific
319 changes as paragraphs below it. ]
323 XXX List any platforms that this version of perl compiles on, that previous
324 versions did not. These will either be enabled by new files in the F<hints/>
325 directories, or new subdirectories and F<README> files at the top level of the
330 =item XXX-some-platform
336 =head2 Discontinued Platforms
338 XXX List any platforms that this version of perl no longer compiles on.
342 =item XXX-some-platform
348 =head2 Platform-Specific Notes
350 XXX List any changes for specific platforms. This could include configuration
351 and compilation changes or changes in portability/compatibility. However,
352 changes within modules for platforms should generally be listed in the
353 L</Modules and Pragmata> section.
357 =item XXX-some-platform
363 =head1 Internal Changes
365 XXX Changes which affect the interface available to C<XS> code go here. Other
366 significant internal changes for future core maintainers should be noted as
369 [ List each change as a =item entry ]
375 The parser no longer gets confused by C<\U=> within a double-quoted string.
376 It used to roduce a syntax error, but now compiles it correctly.
381 =head1 Selected Bug Fixes
383 XXX Important bug fixes in the core language are summarized here. Bug fixes in
384 files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
386 [ List each fix as a =item entry ]
396 Compile-time checking of constant dereferencing (e.g.,
397 C<< my_constant->() >>) has been removed, since it was not taking
398 overloading into account. [perl #69456] [perl #122607]
402 Constant dereferencing now works correctly for typeglob constants.
403 Previously the glob was stringified and its name looked up. Now the glob
404 itself is used. [perl #69456]
408 When parsing a funny character ($ @ % &) followed by braces, the parser no
409 longer tries to guess whether it is a block or a hash constructor (causing
410 a syntax error when it guesses the latter), since it can only be a block.
414 C<undef $reference> now frees the referent immediately, instead of hanging
415 on to it until the next statement. [perl #122556]
419 Various cases where the name of a sub is used (autoload, overloading, error
420 messages) used to crash for lexical subs, but have been fixed.
424 Bareword lookup now tries to avoid vivifying packages if it turns out the
425 bareword is not going to be a subroutine name.
429 Compilation of anonymous constants (e.g., C<sub () { 3 }>) no longer
430 deletes any subroutine named C<__ANON__> in the current package. Not only
431 was C<*__ANON__{CODE}> cleared, but there was a memory leak, too. This bug
432 goes back to perl 5.8.0.
436 Stub declarations like C<sub f;> and C<sub f ();> no longer wipe out
437 constants of the same name declared by C<use constant>. This bug was
438 introduced in perl 5.10.0.
442 Under some conditions a warning raised in compilation of regular
443 expression patterns could be displayed multiple times. This is now
448 =head1 Known Problems
450 XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
451 tests that had to be C<TODO>ed for the release would be noted here. Unfixed
452 platform specific bugs also go here.
454 [ List each fix as a =item entry ]
464 =head1 Errata From Previous Releases
470 XXX Add anything here that we forgot to add, or were mistaken about, in
471 the perldelta of a previous release.
477 XXX If any significant core contributor has died, we've added a short obituary
480 =head1 Acknowledgements
482 XXX Generate this with:
484 perl Porting/acknowledgements.pl v5.21.3..HEAD
486 =head1 Reporting Bugs
488 If you find what you think is a bug, you might check the articles recently
489 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
490 https://rt.perl.org/ . There may also be information at
491 http://www.perl.org/ , the Perl Home Page.
493 If you believe you have an unreported bug, please run the L<perlbug> program
494 included with your release. Be sure to trim your bug down to a tiny but
495 sufficient test case. Your bug report, along with the output of C<perl -V>,
496 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
498 If the bug you are reporting has security implications, which make it
499 inappropriate to send to a publicly archived mailing list, then please send it
500 to perl5-security-report@perl.org. This points to a closed subscription
501 unarchived mailing list, which includes all the core committers, who will be
502 able to help assess the impact of issues, figure out a resolution, and help
503 co-ordinate the release of patches to mitigate or fix the problem across all
504 platforms on which Perl is supported. Please only use this address for
505 security issues in the Perl core, not for modules independently distributed on
510 The F<Changes> file for an explanation of how to view exhaustive details on
513 The F<INSTALL> file for how to build Perl.
515 The F<README> file for general stuff.
517 The F<Artistic> and F<Copying> files for copyright information.