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perldelta: Note bug fix to suppress repeated warnings
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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
39c4a6cf 57=head1 Deprecations
7065301c 58
39c4a6cf 59XXX Any deprecated features, syntax, modules etc. should be listed here.
7065301c 60
39c4a6cf 61=head2 Module removals
b3e82ed1 62
39c4a6cf 63XXX Remove this section if inapplicable.
ca58223b 64
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65The following modules will be removed from the core distribution in a
66future release, and will at that time need to be installed from CPAN.
67Distributions on CPAN which require these modules will need to list them as
68prerequisites.
ca58223b 69
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70The core versions of these modules will now issue C<"deprecated">-category
71warnings to alert you to this fact. To silence these deprecation warnings,
72install the modules in question from CPAN.
23b03637 73
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74Note that these are (with rare exceptions) fine modules that you are encouraged
75to continue to use. Their disinclusion from core primarily hinges on their
76necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
77not usually on concerns over their design.
23b03637 78
39c4a6cf 79=over
85e8fb10 80
39c4a6cf 81=item XXX
85e8fb10 82
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83XXX Note that deprecated modules should be listed here even if they are listed
84as an updated module in the L</Modules and Pragmata> section.
134f90c2 85
39c4a6cf 86=back
134f90c2 87
39c4a6cf 88[ List each other deprecation as a =head2 entry ]
ff433f2d 89
39c4a6cf 90=head1 Performance Enhancements
ff433f2d 91
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92XXX Changes which enhance performance without changing behaviour go here.
93There may well be none in a stable release.
134f90c2 94
39c4a6cf 95[ List each enhancement as a =item entry ]
134f90c2 96
39c4a6cf 97=over 4
7d19f6a1 98
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99=item *
100
39c4a6cf 101XXX
55e8b286 102
39c4a6cf 103=back
55e8b286 104
39c4a6cf 105=head1 Modules and Pragmata
d99849ae 106
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107XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
108go here. If Module::CoreList is updated, generate an initial draft of the
109following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
110for important changes should then be added by hand. In an ideal world,
111dual-life modules would have a F<Changes> file that could be cribbed.
d99849ae 112
39c4a6cf 113[ Within each section, list entries as a =item entry ]
ff433f2d 114
39c4a6cf 115=head2 New Modules and Pragmata
ff433f2d 116
39c4a6cf 117=over 4
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118
119=item *
120
39c4a6cf 121XXX
0bb39c26 122
39c4a6cf 123=back
0bb39c26 124
39c4a6cf 125=head2 Updated Modules and Pragmata
9c97a342 126
39c4a6cf 127=over 4
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128
129=item *
130
39c4a6cf 131L<XXX> has been upgraded from version A.xx to B.yy.
6ab3666b 132
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133=item *
134
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135L<B::Concise> has been upgraded from version 0.992 to 0.993.
136
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137=item *
138
139L<CPAN::Meta::Requirements> has been upgraded from version 2.126 to 2.128.
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140
141=item *
142
143L<ExtUtils::CBuilder> has been upgraded from version 0.280216 to 0.280219.
144[perl #122675].
145
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146=item *
147
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148L<ExtUtils::Manifest> has been upgraded from version 1.65 to 1.66.
149[perl #122415].
150
151=item *
152
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153L<ExtUtils::ParseXS>: Documentation has been added to
154F<ExtUtils-ParseXS/lib/perlxs.pod> concerning handling of locales when writing
155XS code.
156
157=item *
158
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159L<File::Find> has been upgraded from version 1.27 to 1.28.
160
161C<find()> and C<finddepth()> will now warn if passed inappropriate or
162misspelled options.
163
164=item *
165
166L<Getopt::Std> has been upgraded from version 1.10 to 1.11.
167
168=item *
169
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170L<HTTP::Tiny> has been upgraded from version 0.047 to 0.048.
171
172=item *
173
174L<Module::CoreList> has been upgraded from version 5.021003 to 5.021004.
175
176=item *
177
178L<POSIX> has been upgraded from version 1.42 to 1.43.
179
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180The C99 math functions and constants (for example acosh, round,
181M_E, M_PI) have been added.
182
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183=item *
184
185L<Pod::Perldoc> has been upgraded from version 3.23 to 3.24.
186
187=item *
188
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189Scalar-List-Utils has been upgraded from version 1.40 to 1.41.
190
191=item *
192
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193L<constant> has been upgraded from version 1.31 to 1.32.
194
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195It now accepts fully-qualified constant names, allowing constants to be
196defined in packages other than the caller.
197
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198=item *
199
200L<threads> has been upgraded from version 1.95 to 1.96.
201
39c4a6cf 202=back
9c97a342 203
39c4a6cf 204=head2 Removed Modules and Pragmata
d99849ae 205
39c4a6cf 206=over 4
d99849ae 207
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208=item *
209
39c4a6cf 210XXX
ff433f2d 211
13900f93 212=back
aac7f82f 213
13900f93 214=head1 Documentation
aac7f82f 215
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216XXX Changes to files in F<pod/> go here. Consider grouping entries by
217file and be sure to link to the appropriate page, e.g. L<perlfunc>.
6d9b7c7c 218
39c4a6cf 219=head2 New Documentation
2a395b86 220
39c4a6cf 221XXX Changes which create B<new> files in F<pod/> go here.
2a395b86 222
39c4a6cf 223=head3 L<XXX>
2a395b86 224
39c4a6cf 225XXX Description of the purpose of the new file here
2a395b86 226
39c4a6cf 227=head2 Changes to Existing Documentation
2a395b86 228
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229XXX Changes which significantly change existing files in F<pod/> go here.
230However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
231section.
232
233=head3 L<XXX>
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234
235=over 4
236
237=item *
238
39c4a6cf 239XXX Description of the change here
2a395b86 240
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241=item *
242
243L<perlsyn>: An ambiguity in the documentation of the Ellipsis statement has
244been corrected. [perl #122661]
245
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246=back
247
39c4a6cf 248=head1 Diagnostics
2a395b86 249
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250The following additions or changes have been made to diagnostic output,
251including warnings and fatal error messages. For the complete list of
252diagnostic messages, see L<perldiag>.
2a395b86 253
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254XXX New or changed warnings emitted by the core's C<C> code go here. Also
255include any changes in L<perldiag> that reconcile it to the C<C> code.
2a395b86 256
39c4a6cf 257=head2 New Diagnostics
0f4a583b 258
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259XXX Newly added diagnostic messages go under here, separated into New Errors
260and New Warnings
2a395b86 261
39c4a6cf 262=head3 New Errors
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263
264=over 4
265
266=item *
267
39c4a6cf 268XXX L<message|perldiag/"message">
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269
270=back
271
39c4a6cf 272=head3 New Warnings
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273
274=over 4
275
276=item *
277
39c4a6cf 278XXX L<message|perldiag/"message">
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279
280=back
6d9b7c7c 281
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282=head2 Changes to Existing Diagnostics
283
284XXX Changes (i.e. rewording) of diagnostic messages go here
7f55cec0 285
13900f93 286=over 4
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287
288=item *
289
39c4a6cf 290XXX Describe change here
aac7f82f 291
13900f93 292=back
aac7f82f 293
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294=head2 Diagnostic Removals
295
296=over 4
297
298=item *
299
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300"Constant is not a FOO reference"
301
302Compile-time checking of constant dereferencing (e.g.,
303C<< my_constant->() >>) has been removed, since it was not taking
304overloading into account. [perl #69456] [perl #122607]
305
306=item *
307
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308The warning "Ambiguous use of -foo resolved as -&foo()" has been removed.
309There is actually no ambiguity here, and this impedes the use of negated
310constants; e.g., C<-Inf>.
311
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312=item *
313
314The little-known C<my Class $var> syntax (see L<fields> and L<attributes>)
315could get confused in the scope of C<use utf8> if C<Class> were a constant
316whose value contained Latin-1 characters.
317
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318=back
319
39c4a6cf 320=head1 Utility Changes
091fed7c 321
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322XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
323Most of these are built within the directory F<utils>.
902c1f75 324
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325[ List utility changes as a =head2 entry for each utility and =item
326entries for each change
327Use L<XXX> with program names to get proper documentation linking. ]
2901561d 328
39c4a6cf 329=head2 L<XXX>
4594cf53 330
13900f93 331=over 4
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332
333=item *
334
39c4a6cf 335XXX
a1d26ccd 336
39c4a6cf 337=back
a1d26ccd 338
39c4a6cf 339=head1 Configuration and Compilation
7065301c 340
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341XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
342go here. Any other changes to the Perl build process should be listed here.
343However, any platform-specific changes should be listed in the
344L</Platform Support> section, instead.
58f25ac1 345
39c4a6cf 346[ List changes as a =item entry ].
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347
348=over 4
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349
350=item *
351
39c4a6cf 352XXX
a5873648 353
39c4a6cf 354=back
a5873648 355
39c4a6cf 356=head1 Testing
a5873648 357
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358XXX Any significant changes to the testing of a freshly built perl should be
359listed here. Changes which create B<new> files in F<t/> go here as do any
360large changes to the testing harness (e.g. when parallel testing was added).
361Changes to existing files in F<t/> aren't worth summarizing, although the bugs
362that they represent may be covered elsewhere.
a5873648 363
39c4a6cf 364[ List each test improvement as a =item entry ]
a5873648 365
39c4a6cf 366=over 4
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367
368=item *
369
39c4a6cf 370XXX
a5873648 371
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372=back
373
39c4a6cf 374=head1 Platform Support
b10906fb 375
39c4a6cf 376XXX Any changes to platform support should be listed in the sections below.
b10906fb 377
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378[ Within the sections, list each platform as a =item entry with specific
379changes as paragraphs below it. ]
b10906fb 380
39c4a6cf 381=head2 New Platforms
b10906fb 382
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383XXX List any platforms that this version of perl compiles on, that previous
384versions did not. These will either be enabled by new files in the F<hints/>
385directories, or new subdirectories and F<README> files at the top level of the
386source tree.
13900f93 387
7065301c 388=over 4
24a38d90 389
39c4a6cf 390=item XXX-some-platform
24a38d90 391
39c4a6cf 392XXX
bb076206 393
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394=back
395
39c4a6cf 396=head2 Discontinued Platforms
097675bf 397
39c4a6cf 398XXX List any platforms that this version of perl no longer compiles on.
b3211734 399
6e97d65d 400=over 4
b3211734 401
39c4a6cf 402=item XXX-some-platform
7065301c 403
39c4a6cf 404XXX
13900f93 405
39c4a6cf 406=back
7d0ccdba 407
39c4a6cf 408=head2 Platform-Specific Notes
7d0ccdba 409
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410XXX List any changes for specific platforms. This could include configuration
411and compilation changes or changes in portability/compatibility. However,
412changes within modules for platforms should generally be listed in the
413L</Modules and Pragmata> section.
6e97d65d 414
39c4a6cf 415=over 4
6e97d65d 416
39c4a6cf 417=item XXX-some-platform
6e97d65d 418
39c4a6cf 419XXX
7d0ccdba 420
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421=back
422
423=head1 Internal Changes
424
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425XXX Changes which affect the interface available to C<XS> code go here. Other
426significant internal changes for future core maintainers should be noted as
427well.
c9fcb674 428
39c4a6cf 429[ List each change as a =item entry ]
a835cd47 430
39c4a6cf 431=over 4
c1284011 432
7d15b1a8 433XXX
1c43698b 434
6d9b7c7c 435=back
c1284011 436
6d9b7c7c 437=head1 Selected Bug Fixes
375f5f06 438
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439XXX Important bug fixes in the core language are summarized here. Bug fixes in
440files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
441
442[ List each fix as a =item entry ]
443
0346c3a9 444=over 4
375f5f06 445
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446=item *
447
39c4a6cf 448XXX
2884baee 449
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450=item *
451
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452Constant dereferencing now works correctly for typeglob constants.
453Previously the glob was stringified and its name looked up. Now the glob
454itself is used. [perl #69456]
455
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456=item *
457
458When parsing a funny character ($ @ % &) followed by braces, the parser no
459longer tries to guess whether it is a block or a hash constructor (causing
460a syntax error when it guesses the latter), since it can only be a block.
461
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462=item *
463
464C<undef $reference> now frees the referent immediately, instead of hanging
465on to it until the next statement. [perl #122556]
466
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467=item *
468
469Various cases where the name of a sub is used (autoload, overloading, error
470messages) used to crash for lexical subs, but have been fixed.
471
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472=item *
473
474Bareword lookup now tries to avoid vivifying packages if it turns out the
475bareword is not going to be a subroutine name.
476
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477=item *
478
479Compilation of anonymous constants (e.g., C<sub () { 3 }>) no longer
480deletes any subroutine named C<__ANON__> in the current package. Not only
481was C<*__ANON__{CODE}> cleared, but there was a memory leak, too. This bug
482goes back to perl 5.8.0.
483
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484=item *
485
486Stub declarations like C<sub f;> and C<sub f ();> no longer wipe out
487constants of the same name declared by C<use constant>. This bug was
488introduced in perl 5.10.0.
489
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490=item *
491
492Under some conditions a warning raised in compilation of regular
493expression patterns could be displayed multiple times. This is now
494fixed.
495
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496=item *
497
498C<qr/[\N{named sequence}]/> now works properly in many instances. Some
499names known to C<\N{...}> refer to a sequence of multiple characters,
500instead of the usual single character. Bracketed character classes
501generally only match single characters, but now special handling has
502been added so that they can match named sequences, but not if the class
503is inverted or the sequence is specified as the beginning or end of a
504range. In these cases, the only behavior change from before is a slight
505rewording of the fatal error message given when this class is part of a
506C<?[...])> construct. When the C<[...]> stands alone, the same
507non-fatal warning as before is raised, and only the first character in
508the sequence is used, again just as before.
509
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510=item *
511
512Tainted constants evaluated at compile time no longer cause unrelated
513statements to become tainted. [perl #122669]
514
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515=item *
516
517C<open $$fh, ...>, which vivifies a handle with a name like "main::_GEN_0",
518was not giving the handle the right reference count, so a double free could
519happen.
520
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521=item *
522
523When deciding that a bareword was a method name, the parser would get
524confused if an "our" sub with the same name existed, and look up the method
525in the package of the "our" sub, instead of the package of the invocant.
526
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527=item *
528
529The parser no longer gets confused by C<\U=> within a double-quoted string.
530It used to roduce a syntax error, but now compiles it correctly.
531[perl #80368]
532
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533=item *
534
535It has always been the intention for the C<-B> and C<-T> file test
536operators to treat UTF-8 encoded files as text.
537(L<perlfunc|perlfunc/-X FILEHANDLE> has been updated to say this.)
538Previously, it was possible for some files to be considered UTF-8 that
539actually weren't valid UTF-8. This is now fixed. The operators now
540work on EBCDIC platforms as well.
541
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542=item *
543
544Under some conditions warning messages raised during regular expression
545pattern compilation were being output more than once. This has now been
546fixed.
547
39c4a6cf 548=back
b756670b 549
39c4a6cf 550=head1 Known Problems
b756670b 551
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552XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
553tests that had to be C<TODO>ed for the release would be noted here. Unfixed
554platform specific bugs also go here.
e917e94e 555
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556[ List each fix as a =item entry ]
557
558=over 4
e917e94e 559
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560=item *
561
39c4a6cf 562XXX
26dd5fd6 563
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564=back
565
39c4a6cf 566=head1 Errata From Previous Releases
e831f11a 567
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568=over 4
569
570=item *
ff433f2d 571
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572XXX Add anything here that we forgot to add, or were mistaken about, in
573the perldelta of a previous release.
ff433f2d 574
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575=back
576
577=head1 Obituary
ff433f2d 578
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579XXX If any significant core contributor has died, we've added a short obituary
580here.
ff433f2d 581
39c4a6cf 582=head1 Acknowledgements
ff433f2d 583
39c4a6cf 584XXX Generate this with:
e831f11a 585
39c4a6cf 586 perl Porting/acknowledgements.pl v5.21.3..HEAD
f5b73711 587
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588=head1 Reporting Bugs
589
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590If you find what you think is a bug, you might check the articles recently
591posted to the comp.lang.perl.misc newsgroup and the perl bug database at
238894db 592https://rt.perl.org/ . There may also be information at
7ef8b31d 593http://www.perl.org/ , the Perl Home Page.
44691e6f 594
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595If you believe you have an unreported bug, please run the L<perlbug> program
596included with your release. Be sure to trim your bug down to a tiny but
597sufficient test case. Your bug report, along with the output of C<perl -V>,
598will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
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599
600If the bug you are reporting has security implications, which make it
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601inappropriate to send to a publicly archived mailing list, then please send it
602to perl5-security-report@perl.org. This points to a closed subscription
603unarchived mailing list, which includes all the core committers, who will be
604able to help assess the impact of issues, figure out a resolution, and help
f9001595 605co-ordinate the release of patches to mitigate or fix the problem across all
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606platforms on which Perl is supported. Please only use this address for
607security issues in the Perl core, not for modules independently distributed on
608CPAN.
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609
610=head1 SEE ALSO
611
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612The F<Changes> file for an explanation of how to view exhaustive details on
613what changed.
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614
615The F<INSTALL> file for how to build Perl.
616
617The F<README> file for general stuff.
618
619The F<Artistic> and F<Copying> files for copyright information.
620
621=cut