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1=encoding utf8
2
3=head1 NAME
4
0302547a 5perldelta - what is new for perl v5.25.1
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2cfe9b50 7=head1 DESCRIPTION
eabfc7bc 8
0302547a 9This document describes differences between the 5.25.0 release and the 5.25.1
4b8803f0 10release.
f3ed8cbf 11
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12If you are upgrading from an earlier release such as 5.24.0, first read
13L<perl5250delta>, which describes differences between 5.24.0 and 5.25.0.
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0302547a 15=head1 Notice
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17XXX Any important notices here
18
19=head1 Core Enhancements
20
21XXX New core language features go here. Summarize user-visible core language
22enhancements. Particularly prominent performance optimisations could go
23here, but most should go in the L</Performance Enhancements> section.
24
25[ List each enhancement as a =head2 entry ]
26
27=head1 Security
28
29XXX Any security-related notices go here. In particular, any security
30vulnerabilities closed should be noted here rather than in the
31L</Selected Bug Fixes> section.
32
33[ List each security issue as a =head2 entry ]
34
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35=head2 require ::Foo::Bar is now illegal.
36
37Formerly, C<require ::Foo::Bar> would try to read F</Foo/Bar.pm>. Now any
38bareword require which starts with a double colon dies instead.
39
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40=head2 Unescaped literal C<"{"> characters in regular expression
41patterns are no longer permissible
42
43You have to now say something like C<"\{"> or C<"[{]"> to specify to
44match a LEFT CURLY BRACKET. This will allow future extensions to the
45language. This restriction is not enforced, nor are there current plans
46to enforce it, if the C<"{"> is the first character in the pattern.
47
48These have been deprecated since v5.16, with a deprecation message
49displayed starting in v5.22.
50
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51=head2 Literal control character variable names are no longer permissible
52
53A variable name may no longer contain a literal control character under
54any circumstances. These previously were allowed in single-character
55names on ASCII platforms, but have been deprecated there since Perl
56v5.20. This affects things like C<$I<\cT>>, where I<\cT> is a literal
57control (such as a C<NAK> or C<NEGATIVE ACKNOWLEDGE> character) in the
58source code.
0302547a 59
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60=head2 C<qr//xx> is no longer permissible
61
62Using more than one C</x> regular expression pattern modifier on a
63single pattern is now forbidden. This is to allow a future enhancement
64to the language. This usage has been deprecated since v5.22.
65
61463a3e 66=head2 C<NBSP> is no longer permissible in C<\N{...}>
0302547a 67
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68The name of a character may no longer contain non-breaking spaces. It
69has been deprecated to do so since Perl v5.22.
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70
71=head1 Deprecations
72
73XXX Any deprecated features, syntax, modules etc. should be listed here.
74
75=head2 Module removals
76
77XXX Remove this section if inapplicable.
78
79The following modules will be removed from the core distribution in a
80future release, and will at that time need to be installed from CPAN.
81Distributions on CPAN which require these modules will need to list them as
82prerequisites.
83
84The core versions of these modules will now issue C<"deprecated">-category
85warnings to alert you to this fact. To silence these deprecation warnings,
86install the modules in question from CPAN.
87
88Note that these are (with rare exceptions) fine modules that you are encouraged
89to continue to use. Their disinclusion from core primarily hinges on their
90necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
91not usually on concerns over their design.
92
93=over
94
95=item XXX
96
97XXX Note that deprecated modules should be listed here even if they are listed
98as an updated module in the L</Modules and Pragmata> section.
99
100=back
101
102[ List each other deprecation as a =head2 entry ]
103
104=head1 Performance Enhancements
105
106XXX Changes which enhance performance without changing behaviour go here.
107There may well be none in a stable release.
108
109[ List each enhancement as a =item entry ]
110
111=over 4
112
113=item *
114
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115Bareword constant strings are now permitted to take part in constant
116folding. They were originally exempted from constant folding in August 1999,
117during the development of Perl 5.6, to ensure that C<use strict "subs">
118would still apply to bareword constants. That has now been accomplished a
119different way, so barewords, like other constants, now gain the performance
120benefits of constant folding.
121
122This also means that void-context warnings on constant expressions of
123barewords now report the folded constant operand, rather than the operation;
124this matches the behaviour for non-bareword constants.
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125
126=back
127
128=head1 Modules and Pragmata
129
130XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
131go here. If Module::CoreList is updated, generate an initial draft of the
132following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
133for important changes should then be added by hand. In an ideal world,
134dual-life modules would have a F<Changes> file that could be cribbed.
135
136[ Within each section, list entries as a =item entry ]
137
138=head2 New Modules and Pragmata
139
140=over 4
141
142=item *
143
144XXX
145
146=back
147
148=head2 Updated Modules and Pragmata
149
150=over 4
151
152=item *
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153
154L<POSIX> has been upgraded from version 1.68 to 1.69. This remedies several
155defects in making its symbols exportable. [perl #127821]
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156
157=back
158
159=head2 Removed Modules and Pragmata
160
161=over 4
162
163=item *
164
165XXX
166
167=back
168
169=head1 Documentation
170
171XXX Changes to files in F<pod/> go here. Consider grouping entries by
172file and be sure to link to the appropriate page, e.g. L<perlfunc>.
173
174=head2 New Documentation
175
176XXX Changes which create B<new> files in F<pod/> go here.
177
178=head3 L<XXX>
179
180XXX Description of the purpose of the new file here
181
182=head2 Changes to Existing Documentation
183
184XXX Changes which significantly change existing files in F<pod/> go here.
185However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
186section.
187
188=head3 L<XXX>
189
190=over 4
191
192=item *
193
194XXX Description of the change here
195
196=back
197
198=head1 Diagnostics
199
200The following additions or changes have been made to diagnostic output,
201including warnings and fatal error messages. For the complete list of
202diagnostic messages, see L<perldiag>.
203
204XXX New or changed warnings emitted by the core's C<C> code go here. Also
205include any changes in L<perldiag> that reconcile it to the C<C> code.
206
207=head2 New Diagnostics
208
209XXX Newly added diagnostic messages go under here, separated into New Errors
210and New Warnings
211
212=head3 New Errors
213
214=over 4
215
216=item *
217
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218L<Bareword in require contains "%s"|perldiag/"Bareword in require contains "%s"">
219
220=item *
221
222L<Bareword in require maps to empty filename|perldiag/"Bareword in require maps to empty filename">
223
224=item *
225
226L<Bareword in require maps to disallowed filename "%s"|perldiag/"Bareword in require maps to disallowed filename "%s"">
227
228=item *
229
230L<Bareword in require must not start with a double-colon: "%s"|perldiag/"Bareword in require must not start with a double-colon: "%s"">
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231
232=back
233
234=head3 New Warnings
235
236=over 4
237
238=item *
239
240XXX L<message|perldiag/"message">
241
242=back
e1ad135d 243
0302547a 244=head2 Changes to Existing Diagnostics
be2c0c65 245
0302547a 246XXX Changes (i.e. rewording) of diagnostic messages go here
be2c0c65 247
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248=over 4
249
250=item *
251
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252Code like C<$x = $x . "a"> was incorrectly failing to yield a
253L<use of uninitialized value|perldiag/"Use of uninitialized value%s">
254warning when C<$x> was a lexical variable with an undefined value. That has
255now been fixed. [perl #127877]
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256
257=back
258
259=head1 Utility Changes
260
261XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
262Most of these are built within the directory F<utils>.
263
264[ List utility changes as a =head2 entry for each utility and =item
265entries for each change
266Use L<XXX> with program names to get proper documentation linking. ]
267
4de751aa 268=head2 L<perlbug>
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269
270=over 4
271
272=item *
273
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274Long lines in the message body are now wrapped at 900 characters, to stay
275well within the 1000-character limit imposed by SMTP mail transfer agents.
276This is particularly likely to be important for the list of arguments to
277C<Configure>, which can readily exceed the limit if, for example, it names
278several non-default installation paths. This change also adds the first unit
279tests for perlbug. [perl #128020]
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280
281=back
282
283=head1 Configuration and Compilation
284
285XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
286go here. Any other changes to the Perl build process should be listed here.
287However, any platform-specific changes should be listed in the
288L</Platform Support> section, instead.
289
290[ List changes as a =item entry ].
291
292=over 4
293
294=item *
295
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296C<Configure> now builds C<miniperl> and C<generate_uudmap> if you
297invoke it with C<-Dusecrosscompiler> but not C<-Dtargethost=somehost>.
298This means you can supply your target platform C<config.sh>, generate
299the headers and proceed to build your cross-target perl. [perl #127234]
0302547a 300
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301=item *
302
303Builds with C<-Accflags=-DPERL_TRACE_OPS> now only dump the operator
304counts when the environment variable C<PERL_TRACE_OPS> to be set to a
305non-zero integer. This allows C<make test> to pass on such a build.
306
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307=item *
308
309When building with GCC 6 and link-time optimization (the C<-flto> option to
310C<gcc>), C<Configure> was treating all probed symbols as present on the
311system, regardless of whether they actually exist. This has been fixed.
312[perl #128131]
313
314=item *
315
316The F<t/test.pl> library is used for internal testing of Perl itself, and
317also copied by several CPAN modules. Some of those modules must work on
318older versions of Perl, so F<t/test.pl> must in turn avoid newer Perl
319features. Compatibility with Perl 5.8 was inadvertently removed some time
320ago; it has now been restored. [perl #128052]
321
322=item *
323
324The build process no longer emits an extra blank line before building each
325"simple" extension (those with only F<*.pm> and F<*.pod> files).
326
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327=back
328
329=head1 Testing
330
331XXX Any significant changes to the testing of a freshly built perl should be
332listed here. Changes which create B<new> files in F<t/> go here as do any
333large changes to the testing harness (e.g. when parallel testing was added).
334Changes to existing files in F<t/> aren't worth summarizing, although the bugs
335that they represent may be covered elsewhere.
336
337[ List each test improvement as a =item entry ]
338
339=over 4
340
341=item *
342
343XXX
344
345=back
346
347=head1 Platform Support
348
349XXX Any changes to platform support should be listed in the sections below.
350
351[ Within the sections, list each platform as a =item entry with specific
352changes as paragraphs below it. ]
353
354=head2 New Platforms
355
356XXX List any platforms that this version of perl compiles on, that previous
357versions did not. These will either be enabled by new files in the F<hints/>
358directories, or new subdirectories and F<README> files at the top level of the
359source tree.
360
361=over 4
362
363=item XXX-some-platform
364
365XXX
366
367=back
368
369=head2 Discontinued Platforms
370
371XXX List any platforms that this version of perl no longer compiles on.
372
373=over 4
374
375=item XXX-some-platform
376
377XXX
378
379=back
380
381=head2 Platform-Specific Notes
382
383XXX List any changes for specific platforms. This could include configuration
384and compilation changes or changes in portability/compatibility. However,
385changes within modules for platforms should generally be listed in the
386L</Modules and Pragmata> section.
387
388=over 4
389
390=item XXX-some-platform
391
392XXX
393
394=back
395
396=head1 Internal Changes
397
398XXX Changes which affect the interface available to C<XS> code go here. Other
399significant internal changes for future core maintainers should be noted as
400well.
401
402[ List each change as a =item entry ]
403
404=over 4
405
406=item *
407
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408Perl is now built with the C<PERL_OP_PARENT> compiler define enabled by
409default. To disable it, use the C<PERL_NO_OP_PARENT> compiler define.
410This flag alters how the C<op_sibling> field is used in C<OP> structures,
411and has been available optionally since perl 5.22.0.
412
413See L<perl5220delta/"Internal Changes"> for more details of what this
414build option does.
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415
416=back
417
418=head1 Selected Bug Fixes
419
420XXX Important bug fixes in the core language are summarized here. Bug fixes in
421files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
422
423[ List each fix as a =item entry ]
424
425=over 4
426
427=item *
428
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429Expressions containing an C<&&> or C<||> operator (or their synonyms C<and>
430and C<or>) were being compiled incorrectly in some cases. If the left-hand
431side consisted of either a negated bareword constant or a negated C<do {}>
432block containing a constant expression, and the right-hand side consisted of
433a negated non-foldable expression, one of the negations was effectively
434ignored. The same was true of C<if> and C<unless> statement modifiers,
435though with the left-hand and right-hand sides swapped. This long-standing
436bug has now been fixed. [perl #127952]
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437
438=back
439
440=head1 Known Problems
441
442XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
443tests that had to be C<TODO>ed for the release would be noted here. Unfixed
444platform specific bugs also go here.
445
446[ List each fix as a =item entry ]
447
448=over 4
449
450=item *
451
452XXX
453
454=back
455
456=head1 Errata From Previous Releases
457
458=over 4
459
460=item *
461
462XXX Add anything here that we forgot to add, or were mistaken about, in
463the perldelta of a previous release.
464
465=back
466
467=head1 Obituary
468
469XXX If any significant core contributor has died, we've added a short obituary
470here.
471
472=head1 Acknowledgements
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0302547a 474Generate this with:
be2c0c65 475
0302547a 476 perl Porting/acknowledgements.pl v5.25.1..HEAD
f5b73711 477
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478=head1 Reporting Bugs
479
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480If you find what you think is a bug, you might check the articles recently
481posted to the comp.lang.perl.misc newsgroup and the perl bug database at
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482L<https://rt.perl.org/> . There may also be information at
483L<http://www.perl.org/> , the Perl Home Page.
44691e6f 484
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485If you believe you have an unreported bug, please run the L<perlbug> program
486included with your release. Be sure to trim your bug down to a tiny but
487sufficient test case. Your bug report, along with the output of C<perl -V>,
488will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
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490If the bug you are reporting has security implications which make it
491inappropriate to send to a publicly archived mailing list, then see
492L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
493for details of how to report the issue.
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494
495=head1 SEE ALSO
496
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497The F<Changes> file for an explanation of how to view exhaustive details on
498what changed.
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499
500The F<INSTALL> file for how to build Perl.
501
502The F<README> file for general stuff.
503
504The F<Artistic> and F<Copying> files for copyright information.
505
506=cut