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 v5.21.8
12 This document describes differences between the 5.21.7 release and the 5.21.8
15 If you are upgrading from an earlier release such as 5.21.6, first read
16 L<perl5217delta>, which describes differences between 5.21.6 and 5.21.7.
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 ]
30 =head2 The warnings pragma now supports warnings outside of "all"
32 Ever since perl v5.6.0 we've had no way of adding new warnings without
33 retroactively adding them to all existing programs that used C<-w>,
34 C<-W> or C<use warnings>.
36 This caused us to not add new useful warnings out of fear that they
37 might unduly burden users who just wanted to upgrade perl and didn't
38 want to deal with a bunch of warnings from their existing code.
40 We now support a way to have our cake and eat it too, and can add new
41 warnings to the core going forward through other top-level warning
42 categories. See L<the warnings documentation|warnings/Top-level
43 warning categories & associated confusion> for details.
45 =head2 Non-Capturing Regular Expression Flag
47 Regular expressions now support a C</n> flag that disables capturing
48 and filling in C<$1>, C<$2>, etc... inside of groups:
50 "hello" =~ /(hi|hello)/n; # $1 is not set
52 This is equivalent to putting C<?:> at the beginning of every capturing group.
54 See L<perlre/"n"> for more information.
58 XXX Any security-related notices go here. In particular, any security
59 vulnerabilities closed should be noted here rather than in the
60 L</Selected Bug Fixes> section.
62 [ List each security issue as a =head2 entry ]
64 =head1 Incompatible Changes
66 XXX For a release on a stable branch, this section aspires to be:
68 There are no changes intentionally incompatible with 5.XXX.XXX
69 If any exist, they are bugs, and we request that you submit a
70 report. See L</Reporting Bugs> below.
72 [ List each incompatible change as a =head2 entry ]
76 XXX Any deprecated features, syntax, modules etc. should be listed here.
78 =head2 Module removals
80 XXX Remove this section if inapplicable.
82 The following modules will be removed from the core distribution in a
83 future release, and will at that time need to be installed from CPAN.
84 Distributions on CPAN which require these modules will need to list them as
87 The core versions of these modules will now issue C<"deprecated">-category
88 warnings to alert you to this fact. To silence these deprecation warnings,
89 install the modules in question from CPAN.
91 Note that these are (with rare exceptions) fine modules that you are encouraged
92 to continue to use. Their disinclusion from core primarily hinges on their
93 necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
94 not usually on concerns over their design.
100 XXX Note that deprecated modules should be listed here even if they are listed
101 as an updated module in the L</Modules and Pragmata> section.
105 [ List each other deprecation as a =head2 entry ]
107 =head1 Performance Enhancements
109 XXX Changes which enhance performance without changing behaviour go here.
110 There may well be none in a stable release.
112 [ List each enhancement as a =item entry ]
122 =head1 Modules and Pragmata
124 XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
125 go here. If Module::CoreList is updated, generate an initial draft of the
126 following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
127 for important changes should then be added by hand. In an ideal world,
128 dual-life modules would have a F<Changes> file that could be cribbed.
130 [ Within each section, list entries as a =item entry ]
132 =head2 New Modules and Pragmata
142 =head2 Updated Modules and Pragmata
148 L<XXX> has been upgraded from version A.xx to B.yy.
152 L<B> has been upgraded from version 1.54 to 1.55.
154 A bug where, after an ithread creation or psuedofork, special/immortal SVs in
155 the child ithread/psuedoprocess did not have the correct class of
156 C<B::SPECIAL>, has been fixed.
160 =head2 Removed Modules and Pragmata
172 XXX Changes to files in F<pod/> go here. Consider grouping entries by
173 file and be sure to link to the appropriate page, e.g. L<perlfunc>.
175 =head2 New Documentation
177 XXX Changes which create B<new> files in F<pod/> go here.
181 XXX Description of the purpose of the new file here
183 =head2 Changes to Existing Documentation
185 XXX Changes which significantly change existing files in F<pod/> go here.
186 However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
195 XXX Description of the change here
201 The following additions or changes have been made to diagnostic output,
202 including warnings and fatal error messages. For the complete list of
203 diagnostic messages, see L<perldiag>.
205 XXX New or changed warnings emitted by the core's C<C> code go here. Also
206 include any changes in L<perldiag> that reconcile it to the C<C> code.
208 =head2 New Diagnostics
210 XXX Newly added diagnostic messages go under here, separated into New Errors
219 XXX L<message|perldiag/"message">
229 XXX L<message|perldiag/"message">
233 L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">
237 =head2 Changes to Existing Diagnostics
239 XXX Changes (i.e. rewording) of diagnostic messages go here
245 XXX Describe change here
248 L<Locale '%s' may not work well.%s|perldiag/"Locale '%s' may not work well.%s">
249 is no longer raised unless the problemtatic locale is actually used in
250 the Perl program. Previously it was raised if it merely was the
251 underlying locale. All Perl programs have an underlying locale at all
252 times, but something like a C<S<use locale>> is needed for that locale
253 to actually have some effect. This message will not be raised when
254 the underlying locale is hidden.
258 =head1 Utility Changes
260 XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
261 Most of these are built within the directory F<utils>.
263 [ List utility changes as a =head2 entry for each utility and =item
264 entries for each change
265 Use L<XXX> with program names to get proper documentation linking. ]
277 =head1 Configuration and Compilation
279 XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
280 go here. Any other changes to the Perl build process should be listed here.
281 However, any platform-specific changes should be listed in the
282 L</Platform Support> section, instead.
284 [ List changes as a =item entry ].
296 XXX Any significant changes to the testing of a freshly built perl should be
297 listed here. Changes which create B<new> files in F<t/> go here as do any
298 large changes to the testing harness (e.g. when parallel testing was added).
299 Changes to existing files in F<t/> aren't worth summarizing, although the bugs
300 that they represent may be covered elsewhere.
302 [ List each test improvement as a =item entry ]
312 =head1 Platform Support
314 XXX Any changes to platform support should be listed in the sections below.
316 [ Within the sections, list each platform as a =item entry with specific
317 changes as paragraphs below it. ]
321 XXX List any platforms that this version of perl compiles on, that previous
322 versions did not. These will either be enabled by new files in the F<hints/>
323 directories, or new subdirectories and F<README> files at the top level of the
328 =item XXX-some-platform
334 =head2 Discontinued Platforms
336 XXX List any platforms that this version of perl no longer compiles on.
340 =item XXX-some-platform
346 =head2 Platform-Specific Notes
348 XXX List any changes for specific platforms. This could include configuration
349 and compilation changes or changes in portability/compatibility. However,
350 changes within modules for platforms should generally be listed in the
351 L</Modules and Pragmata> section.
361 Previously, on Visual C++ for Win64 built Perls only, when compiling every Perl
362 XS module (including CPAN ones) and Perl aware .c file with a 64 bit Visual C++,
363 would uncondtionally have around a dozen warnings from hv_func.h. These
364 warnings have been silenced. GCC all bitness and Visual C++ for Win32 were
371 =head1 Internal Changes
373 XXX Changes which affect the interface available to C<XS> code go here. Other
374 significant internal changes for future core maintainers should be noted as
377 [ List each change as a =item entry ]
383 Added Perl_sv_get_backrefs() to determine if an SV is a weak-referent.
385 Function either returns an SV * of type AV, which contains the set of
386 weakreferences which reference the passed in SV, or a simple RV * which
387 is the only weakref to this item.
391 C<gv_add_by_type> which was added to public API in 5.11.0 but undocumented and
392 shows no CPAN usage has been removed from public API. Please use public API
393 C<GvSVn> C<GvIOn> C<GvAVn> and C<GvHVn> for adding elements to a GV.
397 C<GvSVn> C<GvIOn> C<GvAVn> and C<GvHVn> have been made rvalues, previously they
398 were lvalues. If you are assigning a SV to C<GvSVn> C<GvIOn> C<GvAVn> and
399 C<GvHVn> you are leaking memory. If you want an lvalue, use C<GvSV> C<GvIO>
408 =head1 Selected Bug Fixes
410 XXX Important bug fixes in the core language are summarized here. Bug fixes in
411 files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
413 [ List each fix as a =item entry ]
423 =head1 Known Problems
425 XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
426 tests that had to be C<TODO>ed for the release would be noted here. Unfixed
427 platform specific bugs also go here.
429 [ List each fix as a =item entry ]
439 =head1 Errata From Previous Releases
445 XXX Add anything here that we forgot to add, or were mistaken about, in
446 the perldelta of a previous release.
452 XXX If any significant core contributor has died, we've added a short obituary
455 =head1 Acknowledgements
457 XXX Generate this with:
459 perl Porting/acknowledgements.pl v5.21.7..HEAD
461 =head1 Reporting Bugs
463 If you find what you think is a bug, you might check the articles recently
464 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
465 https://rt.perl.org/ . There may also be information at
466 http://www.perl.org/ , the Perl Home Page.
468 If you believe you have an unreported bug, please run the L<perlbug> program
469 included with your release. Be sure to trim your bug down to a tiny but
470 sufficient test case. Your bug report, along with the output of C<perl -V>,
471 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
473 If the bug you are reporting has security implications, which make it
474 inappropriate to send to a publicly archived mailing list, then please send it
475 to perl5-security-report@perl.org. This points to a closed subscription
476 unarchived mailing list, which includes all the core committers, who will be
477 able to help assess the impact of issues, figure out a resolution, and help
478 co-ordinate the release of patches to mitigate or fix the problem across all
479 platforms on which Perl is supported. Please only use this address for
480 security issues in the Perl core, not for modules independently distributed on
485 The F<Changes> file for an explanation of how to view exhaustive details on
488 The F<INSTALL> file for how to build Perl.
490 The F<README> file for general stuff.
492 The F<Artistic> and F<Copying> files for copyright information.