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1=encoding utf8
2
3=head1 NAME
4
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5[ this is a template for a new perldelta file. Any text flagged as XXX needs
6to be processed before release. ]
7
8perldelta - what is new for perl v5.21.4
c68523cb 9
238894db 10=head1 DESCRIPTION
c68523cb 11
39c4a6cf 12This document describes differences between the 5.21.3 release and the 5.21.4
238894db 13release.
c68523cb 14
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15If you are upgrading from an earlier release such as 5.21.2, first read
16L<perl5213delta>, which describes differences between 5.21.2 and 5.21.3.
7065301c 17
39c4a6cf 18=head1 Notice
7e957246 19
39c4a6cf 20XXX Any important notices here
7e957246 21
39c4a6cf 22=head1 Core Enhancements
f88f10f5 23
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24XXX New core language features go here. Summarize user-visible core language
25enhancements. Particularly prominent performance optimisations could go
26here, but most should go in the L</Performance Enhancements> section.
21f3b41e 27
39c4a6cf 28[ List each enhancement as a =head2 entry ]
f88f10f5 29
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30=head2 Infinity and NaN (not-a-number) handling improved
31
32Floating point values are able to hold the special values infinity
33(also -infinity), and NaN (not-a-number). Now we more robustly recognize
34and propagate the value in computations, and on output normalize them
35to C<Inf> and C<NaN>.
36
019bf663 37See also the L<POSIX> enhancements.
5b319db8 38
0346c3a9 39=head1 Security
7e957246 40
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41XXX Any security-related notices go here. In particular, any security
42vulnerabilities closed should be noted here rather than in the
43L</Selected Bug Fixes> section.
13900f93 44
39c4a6cf 45[ List each security issue as a =head2 entry ]
8bdb3f93 46
13900f93 47=head1 Incompatible Changes
8bdb3f93 48
39c4a6cf 49XXX For a release on a stable branch, this section aspires to be:
1178d2cf 50
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51 There are no changes intentionally incompatible with 5.XXX.XXX
52 If any exist, they are bugs, and we request that you submit a
53 report. See L</Reporting Bugs> below.
1178d2cf 54
39c4a6cf 55[ List each incompatible change as a =head2 entry ]
f6f3144e 56
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57=head2 Changes to the C<*> prototype
58
59The C<*> character in a subroutine's prototype used to allow barewords
60to take precedence over most, but not all subroutines. It was never
61consistent and exhibited buggy behaviour.
62
63Now it has been changed, so subroutines always take precedence over
64barewords, which brings it into conformity with similarly prototyped
65built-in functions:
66
67 sub splat($) { ... }
68 sub foo { ... }
69 splat(foo); # now always splat(foo())
70 splat(bar); # still splat('bar') as before
71 close(foo); # close(foo())
72 close(bar); # close('bar')
73
39c4a6cf 74=head1 Deprecations
7065301c 75
39c4a6cf 76XXX Any deprecated features, syntax, modules etc. should be listed here.
7065301c 77
39c4a6cf 78=head2 Module removals
b3e82ed1 79
39c4a6cf 80XXX Remove this section if inapplicable.
ca58223b 81
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82The following modules will be removed from the core distribution in a
83future release, and will at that time need to be installed from CPAN.
84Distributions on CPAN which require these modules will need to list them as
85prerequisites.
ca58223b 86
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87The core versions of these modules will now issue C<"deprecated">-category
88warnings to alert you to this fact. To silence these deprecation warnings,
89install the modules in question from CPAN.
23b03637 90
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91Note that these are (with rare exceptions) fine modules that you are encouraged
92to continue to use. Their disinclusion from core primarily hinges on their
93necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
94not usually on concerns over their design.
23b03637 95
39c4a6cf 96=over
85e8fb10 97
39c4a6cf 98=item XXX
85e8fb10 99
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100XXX Note that deprecated modules should be listed here even if they are listed
101as an updated module in the L</Modules and Pragmata> section.
134f90c2 102
39c4a6cf 103=back
134f90c2 104
39c4a6cf 105[ List each other deprecation as a =head2 entry ]
ff433f2d 106
39c4a6cf 107=head1 Performance Enhancements
ff433f2d 108
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109XXX Changes which enhance performance without changing behaviour go here.
110There may well be none in a stable release.
134f90c2 111
39c4a6cf 112[ List each enhancement as a =item entry ]
134f90c2 113
39c4a6cf 114=over 4
7d19f6a1 115
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116=item *
117
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118Subroutines with an empty prototype and bodies containing just C<undef> are
119now eligible for inlining. [perl #122728]
55e8b286 120
39c4a6cf 121=back
55e8b286 122
39c4a6cf 123=head1 Modules and Pragmata
d99849ae 124
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125XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
126go here. If Module::CoreList is updated, generate an initial draft of the
127following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
128for important changes should then be added by hand. In an ideal world,
129dual-life modules would have a F<Changes> file that could be cribbed.
d99849ae 130
39c4a6cf 131[ Within each section, list entries as a =item entry ]
ff433f2d 132
39c4a6cf 133=head2 New Modules and Pragmata
ff433f2d 134
39c4a6cf 135=over 4
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136
137=item *
138
39c4a6cf 139XXX
0bb39c26 140
39c4a6cf 141=back
0bb39c26 142
39c4a6cf 143=head2 Updated Modules and Pragmata
9c97a342 144
39c4a6cf 145=over 4
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146
147=item *
148
39c4a6cf 149L<XXX> has been upgraded from version A.xx to B.yy.
6ab3666b 150
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151=item *
152
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153L<B::Concise> has been upgraded from version 0.992 to 0.993.
154
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155=item *
156
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157L<B::Deparse> has been upgraded from version 1.27 to 1.28.
158
159It now deparses C<our(I<LIST>)> and typed lexical (C<my Dog $spot>)
160correctly.
161
162=item *
163
608e531f 164L<CPAN::Meta::Requirements> has been upgraded from version 2.126 to 2.128.
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165
166=item *
167
168L<ExtUtils::CBuilder> has been upgraded from version 0.280216 to 0.280219.
169[perl #122675].
170
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171=item *
172
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173L<ExtUtils::Manifest> has been upgraded from version 1.65 to 1.66.
174[perl #122415].
175
176=item *
177
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178L<ExtUtils::ParseXS>: Documentation has been added to
179F<ExtUtils-ParseXS/lib/perlxs.pod> concerning handling of locales when writing
180XS code.
181
182=item *
183
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184L<File::Find> has been upgraded from version 1.27 to 1.28.
185
186C<find()> and C<finddepth()> will now warn if passed inappropriate or
187misspelled options.
188
189=item *
190
191L<Getopt::Std> has been upgraded from version 1.10 to 1.11.
192
193=item *
194
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195L<HTTP::Tiny> has been upgraded from version 0.047 to 0.048.
196
197=item *
198
199L<Module::CoreList> has been upgraded from version 5.021003 to 5.021004.
200
201=item *
202
203L<POSIX> has been upgraded from version 1.42 to 1.43.
204
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205The C99 math functions and constants (for example acosh, round,
206M_E, M_PI) have been added.
207
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208=item *
209
210L<Pod::Perldoc> has been upgraded from version 3.23 to 3.24.
211
212=item *
213
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214Scalar-List-Utils has been upgraded from version 1.40 to 1.41.
215
216=item *
217
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218L<constant> has been upgraded from version 1.31 to 1.32.
219
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220It now accepts fully-qualified constant names, allowing constants to be
221defined in packages other than the caller.
222
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223=item *
224
225L<threads> has been upgraded from version 1.95 to 1.96.
226
39c4a6cf 227=back
9c97a342 228
39c4a6cf 229=head2 Removed Modules and Pragmata
d99849ae 230
39c4a6cf 231=over 4
d99849ae 232
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233=item *
234
39c4a6cf 235XXX
ff433f2d 236
13900f93 237=back
aac7f82f 238
13900f93 239=head1 Documentation
aac7f82f 240
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241XXX Changes to files in F<pod/> go here. Consider grouping entries by
242file and be sure to link to the appropriate page, e.g. L<perlfunc>.
6d9b7c7c 243
39c4a6cf 244=head2 New Documentation
2a395b86 245
39c4a6cf 246XXX Changes which create B<new> files in F<pod/> go here.
2a395b86 247
39c4a6cf 248=head3 L<XXX>
2a395b86 249
39c4a6cf 250XXX Description of the purpose of the new file here
2a395b86 251
39c4a6cf 252=head2 Changes to Existing Documentation
2a395b86 253
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254XXX Changes which significantly change existing files in F<pod/> go here.
255However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
256section.
257
258=head3 L<XXX>
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259
260=over 4
261
262=item *
263
39c4a6cf 264XXX Description of the change here
2a395b86 265
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266=item *
267
268L<perlsyn>: An ambiguity in the documentation of the Ellipsis statement has
269been corrected. [perl #122661]
270
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271=back
272
39c4a6cf 273=head1 Diagnostics
2a395b86 274
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275The following additions or changes have been made to diagnostic output,
276including warnings and fatal error messages. For the complete list of
277diagnostic messages, see L<perldiag>.
2a395b86 278
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279XXX New or changed warnings emitted by the core's C<C> code go here. Also
280include any changes in L<perldiag> that reconcile it to the C<C> code.
2a395b86 281
39c4a6cf 282=head2 New Diagnostics
0f4a583b 283
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284XXX Newly added diagnostic messages go under here, separated into New Errors
285and New Warnings
2a395b86 286
39c4a6cf 287=head3 New Errors
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288
289=over 4
290
291=item *
292
39c4a6cf 293XXX L<message|perldiag/"message">
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294
295=back
296
39c4a6cf 297=head3 New Warnings
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298
299=over 4
300
301=item *
302
39c4a6cf 303XXX L<message|perldiag/"message">
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304
305=back
6d9b7c7c 306
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307=head2 Changes to Existing Diagnostics
308
309XXX Changes (i.e. rewording) of diagnostic messages go here
7f55cec0 310
13900f93 311=over 4
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312
313=item *
314
39c4a6cf 315XXX Describe change here
aac7f82f 316
13900f93 317=back
aac7f82f 318
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319=head2 Diagnostic Removals
320
321=over 4
322
323=item *
324
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325"Constant is not a FOO reference"
326
327Compile-time checking of constant dereferencing (e.g.,
328C<< my_constant->() >>) has been removed, since it was not taking
329overloading into account. [perl #69456] [perl #122607]
330
331=item *
332
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333The warning "Ambiguous use of -foo resolved as -&foo()" has been removed.
334There is actually no ambiguity here, and this impedes the use of negated
335constants; e.g., C<-Inf>.
336
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337=item *
338
339The little-known C<my Class $var> syntax (see L<fields> and L<attributes>)
340could get confused in the scope of C<use utf8> if C<Class> were a constant
341whose value contained Latin-1 characters.
342
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343=back
344
39c4a6cf 345=head1 Utility Changes
091fed7c 346
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347XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
348Most of these are built within the directory F<utils>.
902c1f75 349
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350[ List utility changes as a =head2 entry for each utility and =item
351entries for each change
352Use L<XXX> with program names to get proper documentation linking. ]
2901561d 353
39c4a6cf 354=head2 L<XXX>
4594cf53 355
13900f93 356=over 4
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357
358=item *
359
39c4a6cf 360XXX
a1d26ccd 361
39c4a6cf 362=back
a1d26ccd 363
39c4a6cf 364=head1 Configuration and Compilation
7065301c 365
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366XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
367go here. Any other changes to the Perl build process should be listed here.
368However, any platform-specific changes should be listed in the
369L</Platform Support> section, instead.
58f25ac1 370
39c4a6cf 371[ List changes as a =item entry ].
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372
373=over 4
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374
375=item *
376
39c4a6cf 377XXX
a5873648 378
39c4a6cf 379=back
a5873648 380
39c4a6cf 381=head1 Testing
a5873648 382
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383XXX Any significant changes to the testing of a freshly built perl should be
384listed here. Changes which create B<new> files in F<t/> go here as do any
385large changes to the testing harness (e.g. when parallel testing was added).
386Changes to existing files in F<t/> aren't worth summarizing, although the bugs
387that they represent may be covered elsewhere.
a5873648 388
39c4a6cf 389[ List each test improvement as a =item entry ]
a5873648 390
39c4a6cf 391=over 4
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392
393=item *
394
39c4a6cf 395XXX
a5873648 396
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397=back
398
39c4a6cf 399=head1 Platform Support
b10906fb 400
39c4a6cf 401XXX Any changes to platform support should be listed in the sections below.
b10906fb 402
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403[ Within the sections, list each platform as a =item entry with specific
404changes as paragraphs below it. ]
b10906fb 405
39c4a6cf 406=head2 New Platforms
b10906fb 407
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408XXX List any platforms that this version of perl compiles on, that previous
409versions did not. These will either be enabled by new files in the F<hints/>
410directories, or new subdirectories and F<README> files at the top level of the
411source tree.
13900f93 412
7065301c 413=over 4
24a38d90 414
39c4a6cf 415=item XXX-some-platform
24a38d90 416
39c4a6cf 417XXX
bb076206 418
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419=back
420
39c4a6cf 421=head2 Discontinued Platforms
097675bf 422
39c4a6cf 423XXX List any platforms that this version of perl no longer compiles on.
b3211734 424
6e97d65d 425=over 4
b3211734 426
39c4a6cf 427=item XXX-some-platform
7065301c 428
39c4a6cf 429XXX
13900f93 430
39c4a6cf 431=back
7d0ccdba 432
39c4a6cf 433=head2 Platform-Specific Notes
7d0ccdba 434
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435XXX List any changes for specific platforms. This could include configuration
436and compilation changes or changes in portability/compatibility. However,
437changes within modules for platforms should generally be listed in the
438L</Modules and Pragmata> section.
6e97d65d 439
39c4a6cf 440=over 4
6e97d65d 441
39c4a6cf 442=item XXX-some-platform
6e97d65d 443
39c4a6cf 444XXX
7d0ccdba 445
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446=back
447
448=head1 Internal Changes
449
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450XXX Changes which affect the interface available to C<XS> code go here. Other
451significant internal changes for future core maintainers should be noted as
452well.
c9fcb674 453
39c4a6cf 454[ List each change as a =item entry ]
a835cd47 455
39c4a6cf 456=over 4
c1284011 457
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458C<save_re_context> no longer does anything and has been moved to
459F<mathoms.c>.
1c43698b 460
6d9b7c7c 461=back
c1284011 462
6d9b7c7c 463=head1 Selected Bug Fixes
375f5f06 464
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465XXX Important bug fixes in the core language are summarized here. Bug fixes in
466files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
467
468[ List each fix as a =item entry ]
469
0346c3a9 470=over 4
375f5f06 471
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472=item *
473
39c4a6cf 474XXX
2884baee 475
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476=item *
477
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478Constant dereferencing now works correctly for typeglob constants.
479Previously the glob was stringified and its name looked up. Now the glob
480itself is used. [perl #69456]
481
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482=item *
483
484When parsing a funny character ($ @ % &) followed by braces, the parser no
485longer tries to guess whether it is a block or a hash constructor (causing
486a syntax error when it guesses the latter), since it can only be a block.
487
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488=item *
489
490C<undef $reference> now frees the referent immediately, instead of hanging
491on to it until the next statement. [perl #122556]
492
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493=item *
494
495Various cases where the name of a sub is used (autoload, overloading, error
496messages) used to crash for lexical subs, but have been fixed.
497
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498=item *
499
500Bareword lookup now tries to avoid vivifying packages if it turns out the
501bareword is not going to be a subroutine name.
502
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503=item *
504
505Compilation of anonymous constants (e.g., C<sub () { 3 }>) no longer
506deletes any subroutine named C<__ANON__> in the current package. Not only
507was C<*__ANON__{CODE}> cleared, but there was a memory leak, too. This bug
508goes back to perl 5.8.0.
509
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510=item *
511
512Stub declarations like C<sub f;> and C<sub f ();> no longer wipe out
513constants of the same name declared by C<use constant>. This bug was
514introduced in perl 5.10.0.
515
499333dc
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516=item *
517
518Under some conditions a warning raised in compilation of regular
519expression patterns could be displayed multiple times. This is now
520fixed.
521
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522=item *
523
524C<qr/[\N{named sequence}]/> now works properly in many instances. Some
525names known to C<\N{...}> refer to a sequence of multiple characters,
526instead of the usual single character. Bracketed character classes
527generally only match single characters, but now special handling has
528been added so that they can match named sequences, but not if the class
529is inverted or the sequence is specified as the beginning or end of a
530range. In these cases, the only behavior change from before is a slight
531rewording of the fatal error message given when this class is part of a
532C<?[...])> construct. When the C<[...]> stands alone, the same
533non-fatal warning as before is raised, and only the first character in
534the sequence is used, again just as before.
535
aa292ef2
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536=item *
537
538Tainted constants evaluated at compile time no longer cause unrelated
539statements to become tainted. [perl #122669]
540
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541=item *
542
543C<open $$fh, ...>, which vivifies a handle with a name like "main::_GEN_0",
544was not giving the handle the right reference count, so a double free could
545happen.
546
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547=item *
548
549When deciding that a bareword was a method name, the parser would get
550confused if an "our" sub with the same name existed, and look up the method
551in the package of the "our" sub, instead of the package of the invocant.
552
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553=item *
554
555The parser no longer gets confused by C<\U=> within a double-quoted string.
556It used to roduce a syntax error, but now compiles it correctly.
557[perl #80368]
558
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559=item *
560
561It has always been the intention for the C<-B> and C<-T> file test
562operators to treat UTF-8 encoded files as text.
563(L<perlfunc|perlfunc/-X FILEHANDLE> has been updated to say this.)
564Previously, it was possible for some files to be considered UTF-8 that
565actually weren't valid UTF-8. This is now fixed. The operators now
566work on EBCDIC platforms as well.
567
0064f8cc
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568=item *
569
570Under some conditions warning messages raised during regular expression
571pattern compilation were being output more than once. This has now been
572fixed.
573
6ff8f256
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574=item *
575
576A regression has been fixed that was introduced in v5.20.0 (fixed in
577v5.20.1 as well as here) in which a UTF-8 encoded regular expression
578pattern that contains a single ASCII lowercase letter does not match its
579uppercase counterpart. [perl #122655]
580
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581=item *
582
583Constant folding could incorrectly suppress warnings if lexical warnings
584(C<use warnings> or C<no warnings>) were not in effect and C<$^W> were
585false at compile time and true at run time.
586
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587=item *
588
589Loading UTF8 tables during a regular expression match could cause assertion
590failures under debugging builds if the previous match used the very same
591regular expression. [perl #122747]
592
39c4a6cf 593=back
b756670b 594
39c4a6cf 595=head1 Known Problems
b756670b 596
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597XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
598tests that had to be C<TODO>ed for the release would be noted here. Unfixed
599platform specific bugs also go here.
e917e94e 600
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601[ List each fix as a =item entry ]
602
603=over 4
e917e94e 604
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605=item *
606
39c4a6cf 607XXX
26dd5fd6 608
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609=back
610
39c4a6cf 611=head1 Errata From Previous Releases
e831f11a 612
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613=over 4
614
615=item *
ff433f2d 616
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617XXX Add anything here that we forgot to add, or were mistaken about, in
618the perldelta of a previous release.
ff433f2d 619
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620=back
621
622=head1 Obituary
ff433f2d 623
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624XXX If any significant core contributor has died, we've added a short obituary
625here.
ff433f2d 626
39c4a6cf 627=head1 Acknowledgements
ff433f2d 628
39c4a6cf 629XXX Generate this with:
e831f11a 630
39c4a6cf 631 perl Porting/acknowledgements.pl v5.21.3..HEAD
f5b73711 632
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633=head1 Reporting Bugs
634
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635If you find what you think is a bug, you might check the articles recently
636posted to the comp.lang.perl.misc newsgroup and the perl bug database at
238894db 637https://rt.perl.org/ . There may also be information at
7ef8b31d 638http://www.perl.org/ , the Perl Home Page.
44691e6f 639
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640If you believe you have an unreported bug, please run the L<perlbug> program
641included with your release. Be sure to trim your bug down to a tiny but
642sufficient test case. Your bug report, along with the output of C<perl -V>,
643will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
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644
645If the bug you are reporting has security implications, which make it
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646inappropriate to send to a publicly archived mailing list, then please send it
647to perl5-security-report@perl.org. This points to a closed subscription
648unarchived mailing list, which includes all the core committers, who will be
649able to help assess the impact of issues, figure out a resolution, and help
f9001595 650co-ordinate the release of patches to mitigate or fix the problem across all
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651platforms on which Perl is supported. Please only use this address for
652security issues in the Perl core, not for modules independently distributed on
653CPAN.
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654
655=head1 SEE ALSO
656
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657The F<Changes> file for an explanation of how to view exhaustive details on
658what changed.
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659
660The F<INSTALL> file for how to build Perl.
661
662The F<README> file for general stuff.
663
664The F<Artistic> and F<Copying> files for copyright information.
665
666=cut