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perldelta: add another hash overhaul cross reference
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1=encoding utf8
2
3=head1 NAME
4
5ed58cbd 5perldelta - what is new for perl v5.18.0
e128ab2c 6
4eabcf70 7=head1 DESCRIPTION
6db9054f 8
e612b5a0 9This document describes differences between the v5.16.0 release and the v5.18.0
e08634c5 10release.
6db9054f 11
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12If you are upgrading from an earlier release such as v5.14.0, first read
13L<perl5160delta>, which describes differences between v5.14.0 and v5.16.0.
3f01b192 14
5ed58cbd 15=head1 Core Enhancements
3f01b192 16
5ed58cbd 17=head2 New mechanism for experimental features
82d98f72 18
5ed58cbd 19Newly-added experimental features will now require this incantation:
82d98f72 20
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21 no warnings "experimental::feature_name";
22 use feature "feature_name"; # would warn without the prev line
23
24There is a new warnings category, called "experimental", containing
25warnings that the L<feature> pragma emits when enabling experimental
26features.
27
28Newly-added experimental features will also be given special warning IDs,
29which consist of "experimental::" followed by the name of the feature. (The
30plan is to extend this mechanism eventually to all warnings, to allow them
31to be enabled or disabled individually, and not just by category.)
32
33By saying
34
35 no warnings "experimental::feature_name";
36
37you are taking responsibility for any breakage that future changes to, or
38removal of, the feature may cause.
39
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40Since some features (like C<~~> or C<my $_>) now emit experimental warnings,
41and you may want to disable them in code that is also run on perls that do not
42recognize these warning categories, consider using the C<if> pragma like this:
43
5c46a73f 44 no if $] >= 5.018, 'warnings', "experimental::feature_name";
1ea0ff56 45
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46Existing experimental features may begin emitting these warnings, too. Please
47consult L<perlexperiment> for information on which features are considered
48experimental.
49
50=head2 Hash overhaul
51
e612b5a0 52Changes to the implementation of hashes in perl v5.18.0 will be one of the most
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53visible changes to the behavior of existing code.
54
8e74b2ed 55By default, two distinct hash variables with identical keys and values may now
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56provide their contents in a different order where it was previously identical.
57
58When encountering these changes, the key to cleaning up from them is to accept
59that B<hashes are unordered collections> and to act accordingly.
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60
61=head3 Hash randomization
62
63The seed used by Perl's hash function is now random. This means that the
64order which keys/values will be returned from functions like C<keys()>,
65C<values()>, and C<each()> will differ from run to run.
66
67This change was introduced to make Perl's hashes more robust to algorithmic
68complexity attacks, and also because we discovered that it exposes hash
69ordering dependency bugs and makes them easier to track down.
70
71Toolchain maintainers might want to invest in additional infrastructure to
72test for things like this. Running tests several times in a row and then
73comparing results will make it easier to spot hash order dependencies in
74code. Authors are strongly encouraged not to expose the key order of
75Perl's hashes to insecure audiences.
76
77Further, every hash has its own iteration order, which should make it much
78more difficult to determine what the current hash seed is.
79
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80=head3 New hash functions
81
e612b5a0 82Perl v5.18 includes support for multiple hash functions, and changed
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83the default (to ONE_AT_A_TIME_HARD), you can choose a different
84algorithm by defining a symbol at compile time. For a current list,
e612b5a0 85consult the F<INSTALL> document. Note that as of Perl v5.18 we can
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86only recommend use of the default or SIPHASH. All the others are
87known to have security issues and are for research purposes only.
5ed58cbd 88
f105b7be 89=head3 PERL_HASH_SEED environment variable now takes a hex value
5ed58cbd 90
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91C<PERL_HASH_SEED> no longer accepts an integer as a parameter;
92instead the value is expected to be a binary value encoded in a hex
93string, such as "0xf5867c55039dc724". This is to make the
94infrastructure support hash seeds of arbitrary lengths, which might
ad94908e 95exceed that of an integer. (SipHash uses a 16 byte seed.)
5ed58cbd 96
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97=head3 PERL_PERTURB_KEYS environment variable added
98
f105b7be 99The C<PERL_PERTURB_KEYS> environment variable allows one to control the level of
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100randomization applied to C<keys> and friends.
101
f105b7be 102When C<PERL_PERTURB_KEYS> is 0, perl will not randomize the key order at all. The
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103chance that C<keys> changes due to an insert will be the same as in previous
104perls, basically only when the bucket size is changed.
105
f105b7be 106When C<PERL_PERTURB_KEYS> is 1, perl will randomize keys in a non-repeatable
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107way. The chance that C<keys> changes due to an insert will be very high. This
108is the most secure and default mode.
109
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110When C<PERL_PERTURB_KEYS> is 2, perl will randomize keys in a repeatable way.
111Repeated runs of the same program should produce the same output every time.
c40c48bb 112
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113C<PERL_HASH_SEED> implies a non-default C<PERL_PERTURB_KEYS> setting. Setting
114C<PERL_HASH_SEED=0> (exactly one 0) implies C<PERL_PERTURB_KEYS=0> (hash key
115randomization disabled); settng C<PERL_HASH_SEED> to any other value implies
116C<PERL_PERTURB_KEYS=2> (deterministic and repeatable hash key randomization).
117Specifying C<PERL_PERTURB_KEYS> explicitly to a different level overrides this
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118behavior.
119
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120=head3 Hash::Util::hash_seed() now returns a string
121
122Hash::Util::hash_seed() now returns a string instead of an integer. This
123is to make the infrastructure support hash seeds of arbitrary lengths
ad94908e 124which might exceed that of an integer. (SipHash uses a 16 byte seed.)
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125
126=head3 Output of PERL_HASH_SEED_DEBUG has been changed
127
128The environment variable PERL_HASH_SEED_DEBUG now makes perl show both the
f105b7be 129hash function perl was built with, I<and> the seed, in hex, in use for that
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130process. Code parsing this output, should it exist, must change to accommodate
131the new format. Example of the new format:
132
133 $ PERL_HASH_SEED_DEBUG=1 ./perl -e1
134 HASH_FUNCTION = MURMUR3 HASH_SEED = 0x1476bb9f
135
136=head2 Upgrade to Unicode 6.2
137
2e7bc647 138Perl now supports Unicode 6.2. A list of changes from Unicode
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1396.1 is at L<http://www.unicode.org/versions/Unicode6.2.0>.
140
141=head2 Character name aliases may now include non-Latin1-range characters
142
143It is possible to define your own names for characters for use in
144C<\N{...}>, C<charnames::vianame()>, etc. These names can now be
145comprised of characters from the whole Unicode range. This allows for
146names to be in your native language, and not just English. Certain
147restrictions apply to the characters that may be used (you can't define
148a name that has punctuation in it, for example). See L<charnames/CUSTOM
149ALIASES>.
150
151=head2 New DTrace probes
152
153The following new DTrace probes have been added:
14731ad1 154
337fb649 155=over 4
14731ad1 156
82d98f72 157=item *
14731ad1 158
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159C<op-entry>
160
161=item *
162
163C<loading-file>
164
165=item *
166
167C<loaded-file>
168
169=back
170
171=head2 C<${^LAST_FH}>
172
173This new variable provides access to the filehandle that was last read.
174This is the handle used by C<$.> and by C<tell> and C<eof> without
175arguments.
176
177=head2 Regular Expression Set Operations
178
179This is an B<experimental> feature to allow matching against the union,
180intersection, etc., of sets of code points, similar to
181L<Unicode::Regex::Set>. It can also be used to extend C</x> processing
182to [bracketed] character classes, and as a replacement of user-defined
183properties, allowing more complex expressions than they do. See
184L<perlrecharclass/Extended Bracketed Character Classes>.
185
186=head2 Lexical subroutines
187
188This new feature is still considered B<experimental>. To enable it:
189
190 use 5.018;
191 no warnings "experimental::lexical_subs";
192 use feature "lexical_subs";
193
194You can now declare subroutines with C<state sub foo>, C<my sub foo>, and
195C<our sub foo>. (C<state sub> requires that the "state" feature be
196enabled, unless you write it as C<CORE::state sub foo>.)
197
198C<state sub> creates a subroutine visible within the lexical scope in which
199it is declared. The subroutine is shared between calls to the outer sub.
200
201C<my sub> declares a lexical subroutine that is created each time the
202enclosing block is entered. C<state sub> is generally slightly faster than
203C<my sub>.
204
205C<our sub> declares a lexical alias to the package subroutine of the same
206name.
207
208For more information, see L<perlsub/Lexical Subroutines>.
209
210=head2 Computed Labels
211
212The loop controls C<next>, C<last> and C<redo>, and the special C<dump>
213operator, now allow arbitrary expressions to be used to compute labels at run
214time. Previously, any argument that was not a constant was treated as the
215empty string.
216
217=head2 More CORE:: subs
218
219Several more built-in functions have been added as subroutines to the
220CORE:: namespace - namely, those non-overridable keywords that can be
221implemented without custom parsers: C<defined>, C<delete>, C<exists>,
222C<glob>, C<pos>, C<protoytpe>, C<scalar>, C<split>, C<study>, and C<undef>.
223
224As some of these have prototypes, C<prototype('CORE::...')> has been
225changed to not make a distinction between overridable and non-overridable
226keywords. This is to make C<prototype('CORE::pos')> consistent with
227C<prototype(&CORE::pos)>.
228
229=head2 C<kill> with negative signal names
230
231C<kill> has always allowed a negative signal number, which kills the
232process group instead of a single process. It has also allowed signal
233names. But it did not behave consistently, because negative signal names
234were treated as 0. Now negative signals names like C<-INT> are supported
235and treated the same way as -2 [perl #112990].
236
237=head1 Security
238
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239=head2 See also: hash overhaul
240
241Some of the changes in the L<hash overhaul|/"Hash overhaul"> were made to
242enhance security. Please read that section.
243
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244=head2 C<Storable> security warning in documentation
245
246The documentation for C<Storable> now includes a section which warns readers
247of the danger of accepting Storable documents from untrusted sources. The
248short version is that deserializing certain types of data can lead to loading
249modules and other code execution. This is documented behavior and wanted
250behavior, but this opens an attack vector for malicious entities.
251
252=head2 C<Locale::Maketext> allowed code injection via a malicious template
253
254If users could provide a translation string to Locale::Maketext, this could be
255used to invoke arbitrary Perl subroutines available in the current process.
256
257This has been fixed, but it is still possible to invoke any method provided by
258C<Locale::Maketext> itself or a subclass that you are using. One of these
259methods in turn will invoke the Perl core's C<sprintf> subroutine.
260
261In summary, allowing users to provide translation strings without auditing
262them is a bad idea.
263
264This vulnerability is documented in CVE-2012-6329.
265
266=head2 Avoid calling memset with a negative count
267
268Poorly written perl code that allows an attacker to specify the count to perl's
269C<x> string repeat operator can already cause a memory exhaustion
e612b5a0 270denial-of-service attack. A flaw in versions of perl before v5.15.5 can escalate
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271that into a heap buffer overrun; coupled with versions of glibc before 2.16, it
272possibly allows the execution of arbitrary code.
273
274The flaw addressed to this commit has been assigned identifier CVE-2012-5195
275and was researched by Tim Brown.
276
277=head1 Incompatible Changes
278
279=head2 See also: hash overhaul
280
281Some of the changes in the L<hash overhaul|/"Hash overhaul"> are not fully
282compatible with previous versions of perl. Please read that section.
283
284=head2 An unknown character name in C<\N{...}> is now a syntax error
285
286Previously, it warned, and the Unicode REPLACEMENT CHARACTER was
287substituted. Unicode now recommends that this situation be a syntax
288error. Also, the previous behavior led to some confusing warnings and
289behaviors, and since the REPLACEMENT CHARACTER has no use other than as
290a stand-in for some unknown character, any code that has this problem is
291buggy.
292
293=head2 Formerly deprecated characters in C<\N{}> character name aliases are now errors.
294
295Since v5.12.0, it has been deprecated to use certain characters in
296user-defined C<\N{...}> character names. These now cause a syntax
297error. For example, it is now an error to begin a name with a digit,
298such as in
299
300 my $undraftable = "\N{4F}"; # Syntax error!
301
237b9c6d 302or to have commas anywhere in the name. See L<charnames/CUSTOM ALIASES>.
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303
304=head2 C<\N{BELL}> now refers to U+1F514 instead of U+0007
305
306Unicode 6.0 reused the name "BELL" for a different code point than it
307traditionally had meant. Since Perl v5.14, use of this name still
308referred to U+0007, but would raise a deprecation warning. Now, "BELL"
309refers to U+1F514, and the name for U+0007 is "ALERT". All the
310functions in L<charnames> have been correspondingly updated.
311
312=head2 New Restrictions in Multi-Character Case-Insensitive Matching in Regular Expression Bracketed Character Classes
313
314Unicode has now withdrawn their previous recommendation for regular
315expressions to automatically handle cases where a single character can
237b9c6d 316match multiple characters case-insensitively, for example, the letter
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317LATIN SMALL LETTER SHARP S and the sequence C<ss>. This is because
318it turns out to be impracticable to do this correctly in all
319circumstances. Because Perl has tried to do this as best it can, it
320will continue to do so. (We are considering an option to turn it off.)
321However, a new restriction is being added on such matches when they
322occur in [bracketed] character classes. People were specifying
323things such as C</[\0-\xff]/i>, and being surprised that it matches the
324two character sequence C<ss> (since LATIN SMALL LETTER SHARP S occurs in
325this range). This behavior is also inconsistent with using a
326property instead of a range: C<\p{Block=Latin1}> also includes LATIN
327SMALL LETTER SHARP S, but C</[\p{Block=Latin1}]/i> does not match C<ss>.
328The new rule is that for there to be a multi-character case-insensitive
329match within a bracketed character class, the character must be
330explicitly listed, and not as an end point of a range. This more
331closely obeys the Principle of Least Astonishment. See
332L<perlrecharclass/Bracketed Character Classes>. Note that a bug [perl
333#89774], now fixed as part of this change, prevented the previous
334behavior from working fully.
335
336=head2 Explicit rules for variable names and identifiers
337
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338Due to an oversight, single character variable names in v5.16 were
339completely unrestricted. This opened the door to several kinds of
340insanity. As of v5.18, these now follow the rules of other identifiers,
341in addition to accepting characters that match the C<\p{POSIX_Punct}>
342property.
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343
344There are no longer any differences in the parsing of identifiers
345specified as C<$...> or C<${...}>; previously, they were dealt with in
346different parts of the core, and so had slightly different behavior. For
347instance, C<${foo:bar}> was a legal variable name. Since they are now
348both parsed by the same code, that is no longer the case.
349
350=head2 C<\s> in regular expressions now matches a Vertical Tab
351
352No one could recall why C<\s> didn't match C<\cK>, the vertical tab.
353Now it does. Given the extreme rarity of that character, very little
354breakage is expected.
355
356=head2 C</(?{})/> and C</(??{})/> have been heavily reworked
357
358The implementation of this feature has been almost completely rewritten.
359Although its main intent is to fix bugs, some behaviors, especially
360related to the scope of lexical variables, will have changed. This is
361described more fully in the L</Selected Bug Fixes> section.
362
363=head2 Stricter parsing of substitution replacement
364
365It is no longer possible to abuse the way the parser parses C<s///e> like
366this:
367
368 %_=(_,"Just another ");
369 $_="Perl hacker,\n";
370 s//_}->{_/e;print
371
372=head2 C<given> now aliases the global C<$_>
373
374Instead of assigning to an implicit lexical C<$_>, C<given> now makes the
375global C<$_> an alias for its argument, just like C<foreach>. However, it
376still uses lexical C<$_> if there is lexical C<$_> in scope (again, just like
377C<foreach>) [perl #114020].
378
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379=head2 The smartmatch family of features are now experimental
380
381Smart match, added in v5.10.0 and significantly revised in v5.10.1, has been
382a regular point of complaint. Although there are a number of ways in which
383it is useful, it has also proven problematic and confusing for both users and
384implementors of Perl. There have been a number of proposals on how to best
385address the problem. It is clear that smartmatch is almost certainly either
386going to change or go away in the future. Relying on its current behavior
387is not recommended.
388
389Warnings will now be issued when the parser sees C<~~>, C<given>, or C<when>.
390To disable these warnings, you can add this line to the appropriate scope:
391
392 no if $] >= 5.018, "experimental::smartmatch";
393
394Consider, though, replacing the use of these features, as they may change
395behavior again before becoming stable.
396
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397=head2 Lexical C<$_> is now experimental
398
e612b5a0 399Since it was introduced in Perl v5.10, it has caused much confusion with no
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400obvious solution:
401
402=over
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403
404=item *
405
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406Various modules (e.g., List::Util) expect callback routines to use the
407global C<$_>. C<use List::Util 'first'; my $_; first { $_ == 1 } @list>
408does not work as one would expect.
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409
410=item *
411
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412A C<my $_> declaration earlier in the same file can cause confusing closure
413warnings.
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414
415=item *
416
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417The "_" subroutine prototype character allows called subroutines to access
418your lexical C<$_>, so it is not really private after all.
2426c394 419
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420=item *
421
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422Nevertheless, subroutines with a "(@)" prototype and methods cannot access
423the caller's lexical C<$_>, unless they are written in XS.
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424
425=item *
426
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427But even XS routines cannot access a lexical C<$_> declared, not in the
428calling subroutine, but in an outer scope, iff that subroutine happened not
429to mention C<$_> or use any operators that default to C<$_>.
430
431=back
432
433It is our hope that lexical C<$_> can be rehabilitated, but this may
434cause changes in its behavior. Please use it with caution until it
435becomes stable.
436
437=head2 readline() with C<$/ = \N> now reads N characters, not N bytes
438
439Previously, when reading from a stream with I/O layers such as
440C<encoding>, the readline() function, otherwise known as the C<< <> >>
441operator, would read I<N> bytes from the top-most layer. [perl #79960]
442
443Now, I<N> characters are read instead.
444
445There is no change in behaviour when reading from streams with no
446extra layers, since bytes map exactly to characters.
447
448=head2 Overridden C<glob> is now passed one argument
449
450C<glob> overrides used to be passed a magical undocumented second argument
451that identified the caller. Nothing on CPAN was using this, and it got in
452the way of a bug fix, so it was removed. If you really need to identify
453the caller, see L<Devel::Callsite> on CPAN.
454
455=head2 Here-doc parsing
456
457The body of a here-document inside a quote-like operator now always begins
458on the line after the "<<foo" marker. Previously, it was documented to
459begin on the line following the containing quote-like operator, but that
460was only sometimes the case [perl #114040].
461
462=head2 Alphanumeric operators must now be separated from the closing
463delimiter of regular expressions
464
465You may no longer write something like:
466
467 m/a/and 1
468
469Instead you must write
470
471 m/a/ and 1
472
473with whitespace separating the operator from the closing delimiter of
474the regular expression. Not having whitespace has resulted in a
475deprecation warning since Perl v5.14.0.
476
477=head2 qw(...) can no longer be used as parentheses
478
479C<qw> lists used to fool the parser into thinking they were always
480surrounded by parentheses. This permitted some surprising constructions
481such as C<foreach $x qw(a b c) {...}>, which should really be written
482C<foreach $x (qw(a b c)) {...}>. These would sometimes get the lexer into
483the wrong state, so they didn't fully work, and the similar C<foreach qw(a
484b c) {...}> that one might expect to be permitted never worked at all.
485
486This side effect of C<qw> has now been abolished. It has been deprecated
e612b5a0 487since Perl v5.13.11. It is now necessary to use real parentheses
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488everywhere that the grammar calls for them.
489
490=head2 Interaction of lexical and default warnings
491
492Turning on any lexical warnings used first to disable all default warnings
493if lexical warnings were not already enabled:
494
495 $*; # deprecation warning
496 use warnings "void";
497 $#; # void warning; no deprecation warning
498
f105b7be 499Now, the C<debugging>, C<deprecated>, C<glob>, C<inplace> and C<malloc> warnings
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500categories are left on when turning on lexical warnings (unless they are
501turned off by C<no warnings>, of course).
502
503This may cause deprecation warnings to occur in code that used to be free
504of warnings.
505
506Those are the only categories consisting only of default warnings. Default
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507warnings in other categories are still disabled by C<< use warnings "category" >>,
508as we do not yet have the infrastructure for controlling
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509individual warnings.
510
511=head2 C<state sub> and C<our sub>
512
513Due to an accident of history, C<state sub> and C<our sub> were equivalent
514to a plain C<sub>, so one could even create an anonymous sub with
515C<our sub { ... }>. These are now disallowed outside of the "lexical_subs"
516feature. Under the "lexical_subs" feature they have new meanings described
517in L<perlsub/Lexical Subroutines>.
518
519=head2 Defined values stored in environment are forced to byte strings
520
521A value stored in an environment variable has always been stringified. In this
4f5e76eb 522release, it is converted to be only a byte string. First, it is forced to be
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523only a string. Then if the string is utf8 and the equivalent of
524C<utf8::downgrade()> works, that result is used; otherwise, the equivalent of
525C<utf8::encode()> is used, and a warning is issued about wide characters
526(L</Diagnostics>).
527
528=head2 C<require> dies for unreadable files
529
530When C<require> encounters an unreadable file, it now dies. It used to
531ignore the file and continue searching the directories in C<@INC>
532[perl #113422].
533
534=head2 C<gv_fetchmeth_*> and SUPER
535
536The various C<gv_fetchmeth_*> XS functions used to treat a package whose
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537named ended with C<::SUPER> specially. A method lookup on the C<Foo::SUPER>
538package would be treated as a C<SUPER> method lookup on the C<Foo> package. This
539is no longer the case. To do a C<SUPER> lookup, pass the C<Foo> stash and the
540C<GV_SUPER> flag.
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541
542=head2 C<split>'s first argument is more consistently interpreted
543
e612b5a0 544After some changes earlier in v5.17, C<split>'s behavior has been
3853dabd 545simplified: if the PATTERN argument evaluates to a string
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546containing one space, it is treated the way that a I<literal> string
547containing one space once was.
548
549=head1 Deprecations
550
551=head2 Deprecated modules
552
553The following modules will be removed from the core distribution in a
554future release, and should be installed from CPAN instead. Distributions
555on CPAN which require these should add them to their prerequisites.
f105b7be 556The core versions of these modules will issue C<"deprecated">-category
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557warnings.
558
559You can silence these deprecation warnings by installing the modules
560in question from CPAN.
561
562=over
563
564=item L<Archive::Extract>
565
566=item L<B::Lint>
567
568=item L<B::Lint::Debug>
569
570=item L<CPANPLUS> and all included C<CPANPLUS::*> modules
571
572=item L<Devel::InnerPackage>
573
574=item L<encoding>
575
576=item L<Log::Message>
577
578=item L<Log::Message::Config>
579
580=item L<Log::Message::Handlers>
581
582=item L<Log::Message::Item>
583
584=item L<Log::Message::Simple>
585
586=item L<Module::Pluggable>
587
588=item L<Module::Pluggable::Object>
589
590=item L<Object::Accessor>
591
592=item L<Pod::LaTeX>
593
594=item L<Term::UI>
595
596=item L<Term::UI::History>
597
598=back
599
600=head2 Deprecated Utilities
601
602The following utilities will be removed from the core distribution in a
603future release as their associated modules have been deprecated. They
604will remain available with the applicable CPAN distribution.
605
606=over
607
608=item L<cpanp>
609
610=item C<cpanp-run-perl>
611
612=item L<cpan2dist>
613
614These items are part of the C<CPANPLUS> distribution.
615
616=item L<pod2latex>
617
618This item is part of the C<Pod::LaTeX> distribution.
619
620=back
621
622=head2 PL_sv_objcount
623
624This interpreter-global variable used to track the total number of
625Perl objects in the interpreter. It is no longer maintained and will
e612b5a0 626be removed altogether in Perl v5.20.
5ed58cbd
RS
627
628=head2 Five additional characters should be escaped in patterns with C</x>
629
630When a regular expression pattern is compiled with C</x>, Perl treats 6
631characters as white space to ignore, such as SPACE and TAB. However,
632Unicode recommends 11 characters be treated thusly. We will conform
633with this in a future Perl version. In the meantime, use of any of the
634missing characters will raise a deprecation warning, unless turned off.
635The five characters are:
f105b7be 636
c163876c
RS
637 U+0085 NEXT LINE
638 U+200E LEFT-TO-RIGHT MARK
639 U+200F RIGHT-TO-LEFT MARK
640 U+2028 LINE SEPARATOR
641 U+2029 PARAGRAPH SEPARATOR
5ed58cbd
RS
642
643=head2 User-defined charnames with surprising whitespace
644
645A user-defined character name with trailing or multiple spaces in a row is
646likely a typo. This now generates a warning when defined, on the assumption
647that uses of it will be unlikely to include the excess whitespace.
648
649=head2 Various XS-callable functions are now deprecated
650
651All the functions used to classify characters will be removed from a
652future version of Perl, and should not be used. With participating C
653compilers (e.g., gcc), compiling any file that uses any of these will
654generate a warning. These were not intended for public use; there are
655equivalent, faster, macros for most of them.
e612b5a0 656
2e7bc647 657See L<perlapi/Character classes>. The complete list is:
e612b5a0 658
5ed58cbd
RS
659C<is_uni_alnum>, C<is_uni_alnumc>, C<is_uni_alnumc_lc>,
660C<is_uni_alnum_lc>, C<is_uni_alpha>, C<is_uni_alpha_lc>,
661C<is_uni_ascii>, C<is_uni_ascii_lc>, C<is_uni_blank>,
662C<is_uni_blank_lc>, C<is_uni_cntrl>, C<is_uni_cntrl_lc>,
663C<is_uni_digit>, C<is_uni_digit_lc>, C<is_uni_graph>,
664C<is_uni_graph_lc>, C<is_uni_idfirst>, C<is_uni_idfirst_lc>,
665C<is_uni_lower>, C<is_uni_lower_lc>, C<is_uni_print>,
666C<is_uni_print_lc>, C<is_uni_punct>, C<is_uni_punct_lc>,
667C<is_uni_space>, C<is_uni_space_lc>, C<is_uni_upper>,
668C<is_uni_upper_lc>, C<is_uni_xdigit>, C<is_uni_xdigit_lc>,
669C<is_utf8_alnum>, C<is_utf8_alnumc>, C<is_utf8_alpha>,
670C<is_utf8_ascii>, C<is_utf8_blank>, C<is_utf8_char>,
671C<is_utf8_cntrl>, C<is_utf8_digit>, C<is_utf8_graph>,
672C<is_utf8_idcont>, C<is_utf8_idfirst>, C<is_utf8_lower>,
673C<is_utf8_mark>, C<is_utf8_perl_space>, C<is_utf8_perl_word>,
674C<is_utf8_posix_digit>, C<is_utf8_print>, C<is_utf8_punct>,
675C<is_utf8_space>, C<is_utf8_upper>, C<is_utf8_xdigit>,
676C<is_utf8_xidcont>, C<is_utf8_xidfirst>.
677
678In addition these three functions that have never worked properly are
679deprecated:
680C<to_uni_lower_lc>, C<to_uni_title_lc>, and C<to_uni_upper_lc>.
681
f105b7be 682=head2 Certain rare uses of backslashes within regexes are now deprecated
5ed58cbd
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683
684There are three pairs of characters that Perl recognizes as
685metacharacters in regular expression patterns: C<{}>, C<[]>, and C<()>.
686These can be used as well to delimit patterns, as in:
687
688 m{foo}
689 s(foo)(bar)
690
691Since they are metacharacters, they have special meaning to regular
692expression patterns, and it turns out that you can't turn off that
693special meaning by the normal means of preceding them with a backslash,
f105b7be 694if you use them, paired, within a pattern delimited by them. For
5ed58cbd
RS
695example, in
696
697 m{foo\{1,3\}}
698
699the backslashes do not change the behavior, and this matches
700S<C<"f o">> followed by one to three more occurrences of C<"o">.
701
702Usages like this, where they are interpreted as metacharacters, are
703exceedingly rare; we think there are none, for example, in all of CPAN.
704Hence, this deprecation should affect very little code. It does give
705notice, however, that any such code needs to change, which will in turn
706allow us to change the behavior in future Perl versions so that the
707backslashes do have an effect, and without fear that we are silently
708breaking any existing code.
709
d5f315e8
KW
710=head2 Splitting the tokens C<(?> and C<(*> in regular expressions
711
712A deprecation warning is now raised if the C<(> and C<?> are separated
713by white space or comments in C<(?...)> regular expression constructs.
714Similarly, if the C<(> and C<*> are separated in C<(*VERB...)>
715constructs.
716
e0a1dec5
LT
717=head2 Pre-PerlIO IO implementations
718
f3068e1b
RS
719In theory, you can currently build perl without PerlIO. Instead, you'd use a
720wrapper around stdio or sfio. In practice, this isn't very useful. It's not
721well tested, and without any support for IO layers or (thus) Unicode, it's not
722much of a perl. Building without PerlIO will most likely be removed in the
723next version of perl.
724
725PerlIO supports a C<stdio> layer if stdio use is desired. Similarly a
726sfio layer could be produced in the future, if needed.
e0a1dec5 727
5ed58cbd
RS
728=head1 Future Deprecations
729
730=over
71e6aba6
RS
731
732=item *
733
4263dd11 734Platforms without support infrastructure
5ed58cbd
RS
735
736Both Windows CE and z/OS have been historically under-maintained, and are
737currently neither successfully building nor regularly being smoke tested.
738Efforts are underway to change this situation, but it should not be taken for
739granted that the platforms are safe and supported. If they do not become
740buildable and regularly smoked, support for them may be actively removed in
741future releases. If you have an interest in these platforms and you can lend
742your time, expertise, or hardware to help support these platforms, please let
743the perl development effort know by emailing C<perl5-porters@perl.org>.
744
745Some platforms that appear otherwise entirely dead are also on the short list
e612b5a0 746for removal between now and v5.20.0:
5ed58cbd
RS
747
748=over
749
750=item DG/UX
751
752=item NeXT
753
754=back
1993add8 755
ec985017
RS
756We also think it likely that current versions of Perl will no longer
757build AmigaOS, DJGPP, NetWare (natively), OS/2 and Plan 9. If you
758are using Perl on such a platform and have an interest in ensuring
759Perl's future on them, please contact us.
760
761We believe that Perl has long been unable to build on mixed endian
ad94908e 762architectures (such as PDP-11s), and intend to remove any remaining
ec985017
RS
763support code. Similarly, code supporting the long umaintained GNU
764dld will be removed soon if no-one makes themselves known as an
765active user.
766
1993add8
RS
767=item *
768
5ed58cbd
RS
769Swapping of $< and $>
770
064fb797
LT
771Perl has supported the idiom of swapping $< and $> (and likewise $( and
772$)) to temporarily drop permissions since 5.0, like this:
773
774 ($<, $>) = ($>, $<);
775
776However, this idiom modifies the real user/group id, which can have
777undesirable side-effects, is no longer useful on any platform perl
778supports and complicates the implementation of these variables and list
779assignment in general.
780
781As an alternative, assignment only to C<< $> >> is recommended:
782
783 local $> = $<;
784
785See also: L<Setuid Demystified|http://www.cs.berkeley.edu/~daw/papers/setuid-usenix02.pdf>.
71e6aba6
RS
786
787=item *
788
5ed58cbd 789C<microperl>, long broken and of unclear present purpose, will be removed.
71e6aba6
RS
790
791=item *
792
5ed58cbd
RS
793Revamping C<< "\Q" >> semantics in double-quotish strings when combined with
794other escapes.
795
796There are several bugs and inconsistencies involving combinations
797of C<\Q> and escapes like C<\x>, C<\L>, etc., within a C<\Q...\E> pair.
798These need to be fixed, and doing so will necessarily change current
799behavior. The changes have not yet been settled.
71e6aba6 800
d5f315e8
KW
801=item *
802
803Use of C<$^>, where C<^> stands for any actual (non-printing) C0 control
804character will be disallowed in a future Perl version. Use C<${^}>
805instead (where again C<^> stands for a control character),
806or better, C<$^A> , where C<^> this time is a caret (CIRCUMFLEX ACCENT),
807and C<A> stands for any of the characters listed at the end of
808L<perlebcdic/OPERATOR DIFFERENCES>.
809
337fb649 810=back
2426c394 811
5ed58cbd
RS
812=head1 Performance Enhancements
813
814=over 4
2426c394 815
5ed58cbd 816=item *
2426c394 817
5ed58cbd
RS
818Lists of lexical variable declarations (C<my($x, $y)>) are now optimised
819down to a single op and are hence faster than before.
2426c394 820
5ed58cbd 821=item *
2426c394 822
5ed58cbd
RS
823A new C preprocessor define C<NO_TAINT_SUPPORT> was added that, if set,
824disables Perl's taint support altogether. Using the -T or -t command
825line flags will cause a fatal error. Beware that both core tests as
826well as many a CPAN distribution's tests will fail with this change. On
827the upside, it provides a small performance benefit due to reduced
828branching.
2426c394 829
5ed58cbd
RS
830B<Do not enable this unless you know exactly what you are getting yourself
831into.>
832
833=item *
834
835C<pack> with constant arguments is now constant folded in most cases
836[perl #113470].
837
838=item *
839
840Speed up in regular expression matching against Unicode properties. The
841largest gain is for C<\X>, the Unicode "extended grapheme cluster." The
842gain for it is about 35% - 40%. Bracketed character classes, e.g.,
843C<[0-9\x{100}]> containing code points above 255 are also now faster.
844
845=item *
846
847On platforms supporting it, several former macros are now implemented as static
848inline functions. This should speed things up slightly on non-GCC platforms.
849
850=item *
851
66f62cf6
RS
852The optimisation of hashes in boolean context has been extended to
853affect C<scalar(%hash)>, C<%hash ? ... : ...>, and C<sub { %hash || ... }>.
5ed58cbd
RS
854
855=item *
856
f105b7be 857Filetest operators manage the stack in a fractionally more efficient manner.
5ed58cbd
RS
858
859=item *
860
861Globs used in a numeric context are now numified directly in most cases,
f105b7be 862rather than being numified via stringification.
5ed58cbd
RS
863
864=item *
865
866The C<x> repetition operator is now folded to a single constant at compile
867time if called in scalar context with constant operands and no parentheses
868around the left operand.
869
870=back
871
872=head1 Modules and Pragmata
873
874=head2 New Modules and Pragmata
2426c394 875
337fb649 876=over 4
982110e0 877
82d98f72 878=item *
2426c394 879
5ed58cbd
RS
880L<Config::Perl::V> version 0.16 has been added as a dual-lifed module.
881It provides structured data retrieval of C<perl -V> output including
882information only known to the C<perl> binary and not available via L<Config>.
883
884=back
885
886=head2 Updated Modules and Pragmata
887
9863976f 888For a complete list of updates, run:
5ed58cbd 889
f105b7be 890 $ corelist --diff 5.16.0 5.18.0
5ed58cbd 891
e612b5a0 892You can substitute your favorite version in place of C<5.16.0>, too.
5ed58cbd 893
357b01df
AAS
894=over
895
896=item *
897
606e21ea 898L<Archive::Extract> has been upgraded to 0.68.
357b01df
AAS
899
900Work around an edge case on Linux with Busybox's unzip.
901
902=item *
903
606e21ea 904L<Archive::Tar> has been upgraded to 1.90.
357b01df
AAS
905
906ptar now supports the -T option as well as dashless options
907[rt.cpan.org #75473], [rt.cpan.org #75475].
908
909Auto-encode filenames marked as UTF-8 [rt.cpan.org #75474].
910
911Don't use C<tell> on L<IO::Zlib> handles [rt.cpan.org #64339].
912
913Don't try to C<chown> on symlinks.
914
915=item *
916
606e21ea 917L<autodie> has been upgraded to 2.13.
357b01df
AAS
918
919C<autodie> now plays nicely with the 'open' pragma.
920
921=item *
922
606e21ea 923L<B> has been upgraded to 1.42.
357b01df
AAS
924
925The C<stashoff> method of COPs has been added. This provides access to an
926internal field added in perl 5.16 under threaded builds [perl #113034].
927
928C<B::COP::stashpv> now supports UTF-8 package names and embedded NULs.
929
930All C<CVf_*> and C<GVf_*>
931and more SV-related flag values are now provided as constants in the C<B::>
932namespace and available for export. The default export list has not changed.
933
934This makes the module work with the new pad API.
935
936=item *
937
606e21ea 938L<B::Concise> has been upgraded to 0.95.
357b01df
AAS
939
940The C<-nobanner> option has been fixed, and C<format>s can now be dumped.
941When passed a sub name to dump, it will check also to see whether it
942is the name of a format. If a sub and a format share the same name,
943it will dump both.
944
945This adds support for the new C<OpMAYBE_TRUEBOOL> and C<OPpTRUEBOOL> flags.
946
947=item *
948
606e21ea 949L<B::Debug> has been upgraded to 1.18.
357b01df
AAS
950
951This adds support (experimentally) for C<B::PADLIST>, which will be
952added in Perl 5.17.4.
953
954=item *
955
606e21ea 956L<B::Deparse> has been upgraded to 1.20.
357b01df
AAS
957
958Avoid warning when run under C<perl -w>.
959
960It now deparses
961loop controls with the correct precedence, and multiple statements in a
962C<format> line are also now deparsed correctly.
963
964This release suppresses trailing semicolons in formats.
965
966This release adds stub deparsing for lexical subroutines.
967
968It no longer dies when deparsing C<sort> without arguments. It now
969correctly omits the comma for C<system $prog @args> and C<exec $prog
970@args>.
971
972=item *
973
606e21ea 974L<bignum>, L<bigint> and L<bigrat> have been upgraded to 0.33.
357b01df
AAS
975
976The overrides for C<hex> and C<oct> have been rewritten, eliminating
977several problems, and making one incompatible change:
978
979=over
980
981=item *
982
983Formerly, whichever of C<use bigint> or C<use bigrat> was compiled later
984would take precedence over the other, causing C<hex> and C<oct> not to
985respect the other pragma when in scope.
986
987=item *
988
989Using any of these three pragmata would cause C<hex> and C<oct> anywhere
990else in the program to evalute their arguments in list context and prevent
991them from inferring $_ when called without arguments.
992
993=item *
994
995Using any of these three pragmata would make C<oct("1234")> return 1234
996(for any number not beginning with 0) anywhere in the program. Now "1234"
997is translated from octal to decimal, whether within the pragma's scope or
998not.
999
1000=item *
1001
1002The global overrides that facilitate lexical use of C<hex> and C<oct> now
1003respect any existing overrides that were in place before the new overrides
1004were installed, falling back to them outside of the scope of C<use bignum>.
1005
1006=item *
1007
1008C<use bignum "hex">, C<use bignum "oct"> and similar invocations for bigint
1009and bigrat now export a C<hex> or C<oct> function, instead of providing a
1010global override.
1011
1012=back
1013
1014=item *
1015
a0932e7e 1016L<Carp> has been upgraded to 1.29.
357b01df
AAS
1017
1018Carp is no longer confused when C<caller> returns undef for a package that
1019has been deleted.
1020
1021The C<longmess()> and C<shortmess()> functions are now documented.
1022
1023=item *
1024
606e21ea 1025L<CGI> has been upgraded to 3.63.
357b01df
AAS
1026
1027Unrecognized HTML escape sequences are now handled better, problematic
1028trailing newlines are no longer inserted after E<lt>formE<gt> tags
1029by C<startform()> or C<start_form()>, and bogus "Insecure Dependency"
1030warnings appearing with some versions of perl are now worked around.
1031
1032=item *
1033
606e21ea 1034L<Class::Struct> has been upgraded to 0.64.
357b01df
AAS
1035
1036The constructor now respects overridden accessor methods [perl #29230].
1037
1038=item *
1039
606e21ea 1040L<Compress::Raw::Bzip2> has been upgraded to 2.060.
357b01df
AAS
1041
1042The misuse of Perl's "magic" API has been fixed.
1043
1044=item *
1045
606e21ea 1046L<Compress::Raw::Zlib> has been upgraded to 2.060.
357b01df
AAS
1047
1048Upgrade bundled zlib to version 1.2.7.
1049
1050Fix build failures on Irix, Solaris, and Win32, and also when building as C++
1051[rt.cpan.org #69985], [rt.cpan.org #77030], [rt.cpan.org #75222].
1052
1053The misuse of Perl's "magic" API has been fixed.
1054
1055C<compress()>, C<uncompress()>, C<memGzip()> and C<memGunzip()> have
1056been speeded up by making parameter validation more efficient.
1057
1058=item *
1059
606e21ea 1060L<CPAN::Meta::Requirements> has been upgraded to 2.122.
357b01df
AAS
1061
1062Treat undef requirements to C<from_string_hash> as 0 (with a warning).
1063
1064Added C<requirements_for_module> method.
1065
1066=item *
1067
606e21ea 1068L<CPANPLUS> has been upgraded to 0.9135.
357b01df
AAS
1069
1070Allow adding F<blib/script> to PATH.
1071
1072Save the history between invocations of the shell.
1073
1074Handle multiple C<makemakerargs> and C<makeflags> arguments better.
1075
1076This resolves issues with the SQLite source engine.
1077
1078=item *
1079
606e21ea 1080L<Data::Dumper> has been upgraded to 2.145.
357b01df
AAS
1081
1082It has been optimized to only build a seen-scalar hash as necessary,
1083thereby speeding up serialization drastically.
1084
1085Additional tests were added in order to improve statement, branch, condition
1086and subroutine coverage. On the basis of the coverage analysis, some of the
1087internals of Dumper.pm were refactored. Almost all methods are now
1088documented.
1089
1090=item *
1091
606e21ea 1092L<DB_File> has been upgraded to 1.827.
357b01df
AAS
1093
1094The main Perl module no longer uses the C<"@_"> construct.
1095
1096=item *
1097
606e21ea 1098L<Devel::Peek> has been upgraded to 1.11.
357b01df
AAS
1099
1100This fixes compilation with C++ compilers and makes the module work with
1101the new pad API.
1102
1103=item *
1104
606e21ea 1105L<Digest::MD5> has been upgraded to 2.52.
357b01df
AAS
1106
1107Fix C<Digest::Perl::MD5> OO fallback [rt.cpan.org #66634].
1108
1109=item *
1110
606e21ea 1111L<Digest::SHA> has been upgraded to 5.84.
357b01df
AAS
1112
1113This fixes a double-free bug, which might have caused vulnerabilities
1114in some cases.
1115
1116=item *
1117
606e21ea 1118L<DynaLoader> has been upgraded to 1.18.
357b01df
AAS
1119
1120This is due to a minor code change in the XS for the VMS implementation.
1121
1122This fixes warnings about using C<CODE> sections without an C<OUTPUT>
1123section.
1124
1125=item *
1126
606e21ea 1127L<Encode> has been upgraded to 2.49.
357b01df
AAS
1128
1129The Mac alias x-mac-ce has been added, and various bugs have been fixed
1130in Encode::Unicode, Encode::UTF7 and Encode::GSM0338.
1131
1132=item *
1133
606e21ea 1134L<Env> has been upgraded to 1.04.
357b01df
AAS
1135
1136Its SPLICE implementation no longer misbehaves in list context.
1137
1138=item *
1139
606e21ea 1140L<ExtUtils::CBuilder> has been upgraded to 0.280210.
357b01df
AAS
1141
1142Manifest files are now correctly embedded for those versions of VC++ which
1143make use of them. [perl #111782, #111798].
1144
1145A list of symbols to export can now be passed to C<link()> when on
1146Windows, as on other OSes [perl #115100].
1147
1148=item *
1149
606e21ea 1150L<ExtUtils::ParseXS> has been upgraded to 3.18.
357b01df
AAS
1151
1152The generated C code now avoids unnecessarily incrementing
1153C<PL_amagic_generation> on Perl versions where it's done automatically
1154(or on current Perl where the variable no longer exists).
1155
1156This avoids a bogus warning for initialised XSUB non-parameters [perl
1157#112776].
1158
1159=item *
1160
606e21ea 1161L<File::Copy> has been upgraded to 2.26.
357b01df
AAS
1162
1163C<copy()> no longer zeros files when copying into the same directory,
1164and also now fails (as it has long been documented to do) when attempting
1165to copy a file over itself.
1166
1167=item *
1168
606e21ea 1169L<File::DosGlob> has been upgraded to 1.10.
357b01df
AAS
1170
1171The internal cache of file names that it keeps for each caller is now
1172freed when that caller is freed. This means
1173C<< use File::DosGlob 'glob'; eval 'scalar <*>' >> no longer leaks memory.
1174
1175=item *
1176
606e21ea 1177L<File::Fetch> has been upgraded to 0.38.
357b01df
AAS
1178
1179Added the 'file_default' option for URLs that do not have a file
1180component.
1181
1182Use C<File::HomeDir> when available, and provide C<PERL5_CPANPLUS_HOME> to
1183override the autodetection.
1184
1185Always re-fetch F<CHECKSUMS> if C<fetchdir> is set.
1186
1187=item *
1188
606e21ea 1189L<File::Find> has been upgraded to 1.23.
357b01df
AAS
1190
1191This fixes inconsistent unixy path handling on VMS.
1192
1193Individual files may now appear in list of directories to be searched
1194[perl #59750].
1195
1196=item *
1197
606e21ea 1198L<File::Glob> has been upgraded to 1.20.
357b01df
AAS
1199
1200File::Glob has had exactly the same fix as File::DosGlob. Since it is
1201what Perl's own C<glob> operator itself uses (except on VMS), this means
1202C<< eval 'scalar <*>' >> no longer leaks.
1203
1204A space-separated list of patterns return long lists of results no longer
1205results in memory corruption or crashes. This bug was introduced in
1206Perl 5.16.0. [perl #114984]
1207
1208=item *
1209
606e21ea 1210L<File::Spec::Unix> has been upgraded to 3.40.
357b01df
AAS
1211
1212C<abs2rel> could produce incorrect results when given two relative paths or
1213the root directory twice [perl #111510].
1214
1215=item *
1216
606e21ea 1217L<File::stat> has been upgraded to 1.07.
357b01df
AAS
1218
1219C<File::stat> ignores the L<filetest> pragma, and warns when used in
1220combination therewith. But it was not warning for C<-r>. This has been
1221fixed [perl #111640].
1222
1223C<-p> now works, and does not return false for pipes [perl #111638].
1224
1225Previously C<File::stat>'s overloaded C<-x> and C<-X> operators did not give
1226the correct results for directories or executable files when running as
1227root. They had been treating executable permissions for root just like for
1228any other user, performing group membership tests I<etc> for files not owned
1229by root. They now follow the correct Unix behaviour - for a directory they
1230are always true, and for a file if any of the three execute permission bits
1231are set then they report that root can execute the file. Perl's builtin
1232C<-x> and C<-X> operators have always been correct.
1233
1234=item *
1235
606e21ea 1236L<File::Temp> has been upgraded to 0.23
357b01df
AAS
1237
1238Fixes various bugs involving directory removal. Defers unlinking tempfiles if
1239the initial unlink fails, which fixes problems on NFS.
1240
1241=item *
1242
606e21ea 1243L<GDBM_File> has been upgraded to 1.15.
357b01df
AAS
1244
1245The undocumented optional fifth parameter to C<TIEHASH> has been
1246removed. This was intended to provide control of the callback used by
1247C<gdbm*> functions in case of fatal errors (such as filesystem problems),
1248but did not work (and could never have worked). No code on CPAN even
1249attempted to use it. The callback is now always the previous default,
1250C<croak>. Problems on some platforms with how the C<C> C<croak> function
1251is called have also been resolved.
1252
1253=item *
1254
606e21ea 1255L<Hash::Util> has been upgraded to 0.15.
357b01df
AAS
1256
1257C<hash_unlocked> and C<hashref_unlocked> now returns true if the hash is
1258unlocked, instead of always returning false [perl #112126].
1259
1260C<hash_unlocked>, C<hashref_unlocked>, C<lock_hash_recurse> and
1261C<unlock_hash_recurse> are now exportable [perl #112126].
1262
1263Two new functions, C<hash_locked> and C<hashref_locked>, have been added.
1264Oddly enough, these two functions were already exported, even though they
1265did not exist [perl #112126].
1266
1267=item *
1268
606e21ea 1269L<HTTP::Tiny> has been upgraded to 0.025.
357b01df
AAS
1270
1271Add SSL verification features [github #6], [github #9].
1272
1273Include the final URL in the response hashref.
1274
1275Add C<local_address> option.
1276
1277This improves SSL support.
1278
1279=item *
1280
606e21ea 1281L<IO> has been upgraded to 1.28.
357b01df
AAS
1282
1283C<sync()> can now be called on read-only file handles [perl #64772].
1284
1285L<IO::Socket> tries harder to cache or otherwise fetch socket
1286information.
1287
1288=item *
1289
606e21ea 1290L<IPC::Cmd> has been upgraded to 0.80.
357b01df
AAS
1291
1292Use C<POSIX::_exit> instead of C<exit> in C<run_forked> [rt.cpan.org #76901].
1293
1294=item *
1295
606e21ea 1296L<IPC::Open3> has been upgraded to 1.13.
357b01df
AAS
1297
1298The C<open3()> function no longer uses C<POSIX::close()> to close file
1299descriptors since that breaks the ref-counting of file descriptors done by
1300PerlIO in cases where the file descriptors are shared by PerlIO streams,
1301leading to attempts to close the file descriptors a second time when
1302any such PerlIO streams are closed later on.
1303
1304=item *
1305
606e21ea 1306L<Locale::Codes> has been upgraded to 3.25.
357b01df
AAS
1307
1308It includes some new codes.
1309
1310=item *
1311
606e21ea 1312L<Memoize> has been upgraded to 1.03.
357b01df
AAS
1313
1314Fix the C<MERGE> cache option.
1315
1316=item *
1317
606e21ea 1318L<Module::Build> has been upgraded to 0.4003.
357b01df
AAS
1319
1320Fixed bug where modules without C<$VERSION> might have a version of '0' listed
1321in 'provides' metadata, which will be rejected by PAUSE.
1322
1323Fixed bug in PodParser to allow numerals in module names.
1324
1325Fixed bug where giving arguments twice led to them becoming arrays, resulting
1326in install paths like F<ARRAY(0xdeadbeef)/lib/Foo.pm>.
1327
1328A minor bug fix allows markup to be used around the leading "Name" in
1329a POD "abstract" line, and some documentation improvements have been made.
1330
1331=item *
1332
606e21ea 1333L<Module::CoreList> has been upgraded to 2.90
357b01df
AAS
1334
1335Version information is now stored as a delta, which greatly reduces the
1336size of the F<CoreList.pm> file.
1337
1338This restores compatibility with older versions of perl and cleans up
1339the corelist data for various modules.
1340
1341=item *
1342
606e21ea 1343L<Module::Load::Conditional> has been upgraded to 0.54.
357b01df
AAS
1344
1345Fix use of C<requires> on perls installed to a path with spaces.
1346
1347Various enhancements include the new use of Module::Metadata.
1348
1349=item *
1350
606e21ea 1351L<Module::Metadata> has been upgraded to 1.000011.
357b01df
AAS
1352
1353The creation of a Module::Metadata object for a typical module file has
1354been sped up by about 40%, and some spurious warnings about C<$VERSION>s
1355have been suppressed.
1356
1357=item *
1358
606e21ea 1359L<Module::Pluggable> has been upgraded to 4.7.
357b01df
AAS
1360
1361Amongst other changes, triggers are now allowed on events, which gives
1362a powerful way to modify behaviour.
1363
1364=item *
1365
606e21ea 1366L<Net::Ping> has been upgraded to 2.41.
357b01df
AAS
1367
1368This fixes some test failures on Windows.
1369
1370=item *
1371
606e21ea 1372L<Opcode> has been upgraded to 1.25.
357b01df
AAS
1373
1374Reflect the removal of the boolkeys opcode and the addition of the
1375clonecv, introcv and padcv opcodes.
1376
1377=item *
1378
606e21ea 1379L<overload> has been upgraded to 1.22.
357b01df
AAS
1380
1381C<no overload> now warns for invalid arguments, just like C<use overload>.
1382
1383=item *
1384
606e21ea 1385L<PerlIO::encoding> has been upgraded to 0.16.
357b01df
AAS
1386
1387This is the module implementing the ":encoding(...)" I/O layer. It no
1388longer corrupts memory or crashes when the encoding back-end reallocates
1389the buffer or gives it a typeglob or shared hash key scalar.
1390
1391=item *
1392
606e21ea 1393L<PerlIO::scalar> has been upgraded to 0.16.
357b01df
AAS
1394
1395The buffer scalar supplied may now only contain code pounts 0xFF or
1396lower. [perl #109828]
1397
1398=item *
1399
606e21ea 1400L<Perl::OSType> has been upgraded to 1.003.
357b01df
AAS
1401
1402This fixes a bug detecting the VOS operating system.
1403
1404=item *
1405
606e21ea 1406L<Pod::Html> has been upgraded to 1.18.
357b01df
AAS
1407
1408The option C<--libpods> has been reinstated. It is deprecated, and its use
1409does nothing other than issue a warning that it is no longer supported.
1410
1411Since the HTML files generated by pod2html claim to have a UTF-8 charset,
1412actually write the files out using UTF-8 [perl #111446].
1413
1414=item *
1415
606e21ea 1416L<Pod::Simple> has been upgraded to 3.28.
357b01df
AAS
1417
1418Numerous improvements have been made, mostly to Pod::Simple::XHTML,
1419which also has a compatibility change: the C<codes_in_verbatim> option
1420is now disabled by default. See F<cpan/Pod-Simple/ChangeLog> for the
1421full details.
1422
1423=item *
1424
606e21ea 1425L<re> has been upgraded to 0.23
357b01df
AAS
1426
1427Single character [class]es like C</[s]/> or C</[s]/i> are now optimized
1428as if they did not have the brackets, i.e. C</s/> or C</s/i>.
1429
1430See note about C<op_comp> in the L</Internal Changes> section below.
1431
1432=item *
1433
606e21ea 1434L<Safe> has been upgraded to 2.35.
357b01df
AAS
1435
1436Fix interactions with C<Devel::Cover>.
1437
1438Don't eval code under C<no strict>.
1439
1440=item *
1441
606e21ea 1442L<Scalar::Util> has been upgraded to version 1.27.
357b01df
AAS
1443
1444Fix an overloading issue with C<sum>.
1445
1446C<first> and C<reduce> now check the callback first (so C<&first(1)> is
1447disallowed).
1448
1449Fix C<tainted> on magical values [rt.cpan.org #55763].
1450
1451Fix C<sum> on previously magical values [rt.cpan.org #61118].
1452
1453Fix reading past the end of a fixed buffer [rt.cpan.org #72700].
1454
1455=item *
1456
606e21ea 1457L<Search::Dict> has been upgraded to 1.07.
357b01df
AAS
1458
1459No longer require C<stat> on filehandles.
1460
1461Use C<fc> for casefolding.
1462
1463=item *
1464
606e21ea 1465L<Socket> has been upgraded to 2.009.
357b01df
AAS
1466
1467Constants and functions required for IP multicast source group membership
1468have been added.
1469
1470C<unpack_sockaddr_in()> and C<unpack_sockaddr_in6()> now return just the IP
1471address in scalar context, and C<inet_ntop()> now guards against incorrect
1472length scalars being passed in.
1473
1474This fixes an uninitialized memory read.
1475
1476=item *
1477
606e21ea 1478L<Storable> has been upgraded to 2.41.
357b01df
AAS
1479
1480Modifying C<$_[0]> within C<STORABLE_freeze> no longer results in crashes
1481[perl #112358].
1482
1483An object whose class implements C<STORABLE_attach> is now thawed only once
1484when there are multiple references to it in the structure being thawed
1485[perl #111918].
1486
1487Restricted hashes were not always thawed correctly [perl #73972].
1488
1489Storable would croak when freezing a blessed REF object with a
1490C<STORABLE_freeze()> method [perl #113880].
1491
1492It can now freeze and thaw vstrings correctly. This causes a slight
1493incompatible change in the storage format, so the format version has
1494increased to 2.9.
1495
1496This contains various bugfixes, including compatibility fixes for older
1497versions of Perl and vstring handling.
1498
1499=item *
1500
606e21ea 1501L<Sys::Syslog> has been upgraded to 0.32.
357b01df
AAS
1502
1503This contains several bug fixes relating to C<getservbyname()>,
1504C<setlogsock()>and log levels in C<syslog()>, together with fixes for
1505Windows, Haiku-OS and GNU/kFreeBSD. See F<cpan/Sys-Syslog/Changes>
1506for the full details.
1507
1508=item *
1509
606e21ea 1510L<Term::ANSIColor> has been upgraded to 4.02.
357b01df
AAS
1511
1512Add support for italics.
1513
1514Improve error handling.
1515
1516=item *
1517
606e21ea 1518L<Term::ReadLine> has been upgraded to 1.10. This fixes the
357b01df
AAS
1519use of the B<cpan> and B<cpanp> shells on Windows in the event that the current
1520drive happens to contain a F<\dev\tty> file.
1521
1522=item *
1523
606e21ea 1524L<Test::Harness> has been upgraded to 3.26.
357b01df
AAS
1525
1526Fix glob semantics on Win32 [rt.cpan.org #49732].
1527
1528Don't use C<Win32::GetShortPathName> when calling perl [rt.cpan.org #47890].
1529
1530Ignore -T when reading shebang [rt.cpan.org #64404].
1531
1532Handle the case where we don't know the wait status of the test more
1533gracefully.
1534
1535Make the test summary 'ok' line overridable so that it can be changed to a
1536plugin to make the output of prove idempotent.
1537
1538Don't run world-writable files.
1539
1540=item *
1541
606e21ea 1542L<Text::Tabs> and L<Text::Wrap> have been upgraded to
357b01df
AAS
15432012.0818. Support for Unicode combining characters has been added to them
1544both.
1545
1546=item *
1547
606e21ea 1548L<threads::shared> has been upgraded to 1.31.
357b01df
AAS
1549
1550This adds the option to warn about or ignore attempts to clone structures
1551that can't be cloned, as opposed to just unconditionally dying in
1552that case.
1553
1554This adds support for dual-valued values as created by
1555L<Scalar::Util::dualvar|Scalar::Util/"dualvar NUM, STRING">.
1556
1557=item *
1558
606e21ea 1559L<Tie::StdHandle> has been upgraded to 4.3.
357b01df
AAS
1560
1561C<READ> now respects the offset argument to C<read> [perl #112826].
1562
1563=item *
1564
606e21ea 1565L<Time::Local> has been upgraded to 1.2300.
357b01df
AAS
1566
1567Seconds values greater than 59 but less than 60 no longer cause
1568C<timegm()> and C<timelocal()> to croak.
1569
1570=item *
1571
606e21ea 1572L<Unicode::UCD> has been upgraded to 0.53.
357b01df
AAS
1573
1574This adds a function L<all_casefolds()|Unicode::UCD/all_casefolds()>
1575that returns all the casefolds.
1576
1577=item *
1578
606e21ea 1579L<Win32> has been upgraded to 0.47.
357b01df
AAS
1580
1581New APIs have been added for getting and setting the current code page.
1582
1583=back
1584
1585
5ed58cbd
RS
1586=head2 Removed Modules and Pragmata
1587
32b79602 1588=over
33392251
BF
1589
1590=item *
1591
5ed58cbd
RS
1592L<Version::Requirements> has been removed from the core distribution. It is
1593available under a different name: L<CPAN::Meta::Requirements>.
2426c394 1594
337fb649 1595=back
2426c394 1596
5ed58cbd 1597=head1 Documentation
19718730 1598
5ed58cbd
RS
1599=head2 Changes to Existing Documentation
1600
1601=head3 L<perlcheat>
82d98f72 1602
5a6a30f4 1603=over 4
b7c7d786 1604
5ed58cbd
RS
1605=item *
1606
1607L<perlcheat> has been reorganized, and a few new sections were added.
1608
1609=back
1610
1611=head3 L<perldata>
1612
1613=over 4
82d98f72 1614
5ed58cbd 1615=item *
d2d1e842 1616
5ed58cbd
RS
1617Now explicitly documents the behaviour of hash initializer lists that
1618contain duplicate keys.
f355e93d 1619
5a6a30f4 1620=back
f355e93d 1621
5ed58cbd 1622=head3 L<perldiag>
19718730 1623
19718730 1624=over 4
e14ac59b 1625
5ed58cbd
RS
1626=item *
1627
1628The explanation of symbolic references being prevented by "strict refs"
1629now doesn't assume that the reader knows what symbolic references are.
1630
1631=back
9f351b45 1632
5ed58cbd 1633=head3 L<perlfaq>
9f351b45 1634
5ed58cbd 1635=over 4
9f351b45 1636
5ed58cbd 1637=item *
7cf3104f 1638
5ed58cbd 1639L<perlfaq> has been synchronized with version 5.0150040 from CPAN.
12719193 1640
6253ee75 1641=back
216cf7fc 1642
5ed58cbd 1643=head3 L<perlfunc>
f5b73711 1644
5ed58cbd
RS
1645=over 4
1646
1647=item *
a75569c0 1648
5ed58cbd 1649The return value of C<pipe> is now documented.
a75569c0 1650
5ed58cbd 1651=item *
a75569c0 1652
5ed58cbd
RS
1653Clarified documentation of C<our>.
1654
1655=back
1656
1657=head3 L<perlop>
1658
1659=over 4
1660
1661=item *
1662
1663Loop control verbs (C<dump>, C<goto>, C<next>, C<last> and C<redo>) have always
1664had the same precedence as assignment operators, but this was not documented
1665until now.
1666
1667=back
1668
1669=head3 Diagnostics
1670
1671The following additions or changes have been made to diagnostic output,
1672including warnings and fatal error messages. For the complete list of
1673diagnostic messages, see L<perldiag>.
1674
5ed58cbd
RS
1675=head2 New Diagnostics
1676
5ed58cbd
RS
1677=head3 New Errors
1678
1679=over 4
1680
1681=item *
1682
1683L<Unterminated delimiter for here document|perldiag/"Unterminated delimiter for here document">
1684
1685This message now occurs when a here document label has an initial quotation
1686mark but the final quotation mark is missing.
1687
1688This replaces a bogus and misleading error message about not finding the label
1689itself [perl #114104].
1690
1691=item *
1692
1693L<panic: child pseudo-process was never scheduled|perldiag/"panic: child pseudo-process was never scheduled">
1694
1695This error is thrown when a child pseudo-process in the ithreads implementation
1696on Windows was not scheduled within the time period allowed and therefore was
1697not able to initialize properly [perl #88840].
1698
1699=item *
1700
1701L<Group name must start with a non-digit word character in regex; marked by <-- HERE in mE<sol>%sE<sol>|perldiag/"Group name must start with a non-digit word character in regex; marked by <-- HERE in m/%s/">
1702
1703This error has been added for C<(?&0)>, which is invalid. It used to
1704produce an incomprehensible error message [perl #101666].
1705
1706=item *
1707
1708L<Can't use an undefined value as a subroutine reference|perldiag/"Can't use an undefined value as %s reference">
1709
1710Calling an undefined value as a subroutine now produces this error message.
1711It used to, but was accidentally disabled, first in Perl 5.004 for
e612b5a0 1712non-magical variables, and then in Perl v5.14 for magical (e.g., tied)
5ed58cbd
RS
1713variables. It has now been restored. In the mean time, undef was treated
1714as an empty string [perl #113576].
1715
1716=item *
1717
1718L<Experimental "%s" subs not enabled|perldiag/"Experimental "%s" subs not enabled">
1719
1720To use lexical subs, you must first enable them:
1721
1722 no warnings 'experimental::lexical_subs';
1723 use feature 'lexical_subs';
1724 my sub foo { ... }
1725
1726=back
1727
1728=head3 New Warnings
1729
1730=over 4
1731
1732=item *
1733
5cd341ec 1734L<'Strings with code points over 0xFF may not be mapped into in-memory file handles'|perldiag/"Strings with code points over 0xFF may not be mapped into in-memory file handles">
5ed58cbd
RS
1735
1736=item *
1737
1738L<'%s' resolved to '\o{%s}%d'|perldiag/"'%s' resolved to '\o{%s}%d'">
1739
1740=item *
1741
1742L<'Trailing white-space in a charnames alias definition is deprecated'|perldiag/"Trailing white-space in a charnames alias definition is deprecated">
1743
1744=item *
1745
1746L<'A sequence of multiple spaces in a charnames alias definition is deprecated'|perldiag/"A sequence of multiple spaces in a charnames alias definition is deprecated">
1747
1748=item *
1749
1750L<'Passing malformed UTF-8 to "%s" is deprecated'|perldiag/"Passing malformed UTF-8 to "%s" is deprecated">
1751
1752=item *
1753
1754L<Subroutine "&%s" is not available|perldiag/"Subroutine "&%s" is not available">
1755
1756(W closure) During compilation, an inner named subroutine or eval is
1757attempting to capture an outer lexical subroutine that is not currently
1758available. This can happen for one of two reasons. First, the lexical
1759subroutine may be declared in an outer anonymous subroutine that has not
1760yet been created. (Remember that named subs are created at compile time,
1761while anonymous subs are created at run-time.) For example,
1762
1763 sub { my sub a {...} sub f { \&a } }
1764
1765At the time that f is created, it can't capture the current the "a" sub,
1766since the anonymous subroutine hasn't been created yet. Conversely, the
1767following won't give a warning since the anonymous subroutine has by now
1768been created and is live:
1769
1770 sub { my sub a {...} eval 'sub f { \&a }' }->();
1771
1772The second situation is caused by an eval accessing a variable that has
1773gone out of scope, for example,
1774
1775 sub f {
1776 my sub a {...}
1777 sub { eval '\&a' }
1778 }
1779 f()->();
1780
1781Here, when the '\&a' in the eval is being compiled, f() is not currently
1782being executed, so its &a is not available for capture.
1783
1784=item *
1785
1786L<"%s" subroutine &%s masks earlier declaration in same %s|perldiag/"%s" subroutine &%s masks earlier declaration in same %s>
1787
1788(W misc) A "my" or "state" subroutine has been redeclared in the
1789current scope or statement, effectively eliminating all access to
1790the previous instance. This is almost always a typographical error.
1791Note that the earlier subroutine will still exist until the end of
1792the scope or until all closure references to it are destroyed.
1793
1794=item *
1795
1796L<The %s feature is experimental|perldiag/"The %s feature is experimental">
1797
1798(S experimental) This warning is emitted if you enable an experimental
1799feature via C<use feature>. Simply suppress the warning if you want
1800to use the feature, but know that in doing so you are taking the risk
1801of using an experimental feature which may change or be removed in a
1802future Perl version:
1803
1804 no warnings "experimental::lexical_subs";
1805 use feature "lexical_subs";
1806
1807=item *
1808
1809L<sleep(%u) too large|perldiag/"sleep(%u) too large">
1810
1811(W overflow) You called C<sleep> with a number that was larger than it can
1812reliably handle and C<sleep> probably slept for less time than requested.
1813
1814=item *
1815
1816L<Wide character in setenv|perldiag/"Wide character in %s">
1817
1818Attempts to put wide characters into environment variables via C<%ENV> now
1819provoke this warning.
1820
1821=item *
1822
1823"L<Invalid negative number (%s) in chr|perldiag/"Invalid negative number (%s) in chr">"
1824
1825C<chr()> now warns when passed a negative value [perl #83048].
1826
1827=item *
1828
1829"L<Integer overflow in srand|perldiag/"Integer overflow in srand">"
1830
1831C<srand()> now warns when passed a value that doesn't fit in a C<UV> (since the
1832value will be truncated rather than overflowing) [perl #40605].
1833
1834=item *
1835
1836"L<-i used with no filenames on the command line, reading from STDIN|perldiag/"-i used with no filenames on the command line, reading from STDIN">"
1837
1838Running perl with the C<-i> flag now warns if no input files are provided on
1839the command line [perl #113410].
1840
1841=back
1842
1843=head2 Changes to Existing Diagnostics
1844
1845=over 4
1846
1847=item *
1848
1849L<$* is no longer supported|perldiag/"$* is no longer supported">
1850
1851The warning that use of C<$*> and C<$#> is no longer supported is now
1852generated for every location that references them. Previously it would fail
1853to be generated if another variable using the same typeglob was seen first
1854(e.g. C<@*> before C<$*>), and would not be generated for the second and
1855subsequent uses. (It's hard to fix the failure to generate warnings at all
1856without also generating them every time, and warning every time is
1857consistent with the warnings that C<$[> used to generate.)
1858
1859=item *
1860
1861The warnings for C<\b{> and C<\B{> were added. They are a deprecation
1862warning which should be turned off by that category. One should not
1863have to turn off regular regexp warnings as well to get rid of these.
1864
1865=item *
1866
1867L<Constant(%s): Call to &{$^H{%s}} did not return a defined value|perldiag/Constant(%s): Call to &{$^H{%s}} did not return a defined value>
1868
1869Constant overloading that returns C<undef> results in this error message.
1870For numeric constants, it used to say "Constant(undef)". "undef" has been
1871replaced with the number itself.
1872
1873=item *
1874
1875The error produced when a module cannot be loaded now includes a hint that
1876the module may need to be installed: "Can't locate hopping.pm in @INC (you
1877may need to install the hopping module) (@INC contains: ...)"
1878
1879=item *
1880
1881L<vector argument not supported with alpha versions|perldiag/vector argument not supported with alpha versions>
1882
1883This warning was not suppressable, even with C<no warnings>. Now it is
1884suppressible, and has been moved from the "internal" category to the
1885"printf" category.
1886
1887=item *
1888
1889C<< Can't do {n,m} with n > m in regex; marked by <-- HERE in m/%s/ >>
1890
1891This fatal error has been turned into a warning that reads:
1892
1893L<< Quantifier {n,m} with n > m can't match in regex | perldiag/Quantifier {n,m} with n > m can't match in regex >>
1894
1895(W regexp) Minima should be less than or equal to maxima. If you really want
1896your regexp to match something 0 times, just put {0}.
1897
1898=item *
1899
1900The "Runaway prototype" warning that occurs in bizarre cases has been
1901removed as being unhelpful and inconsistent.
1902
1903=item *
1904
1905The "Not a format reference" error has been removed, as the only case in
1906which it could be triggered was a bug.
1907
1908=item *
1909
1910The "Unable to create sub named %s" error has been removed for the same
1911reason.
1912
1913=item *
1914
1915The 'Can't use "my %s" in sort comparison' error has been downgraded to a
1916warning, '"my %s" used in sort comparison' (with 'state' instead of 'my'
1917for state variables). In addition, the heuristics for guessing whether
1918lexical $a or $b has been misused have been improved to generate fewer
1919false positives. Lexical $a and $b are no longer disallowed if they are
1920outside the sort block. Also, a named unary or list operator inside the
1921sort block no longer causes the $a or $b to be ignored [perl #86136].
1922
1923=back
1924
1925=head1 Utility Changes
1926
1927=head3 L<h2xs>
1928
1929=over 4
1930
1931=item *
1932
1933F<h2xs> no longer produces invalid code for empty defines. [perl #20636]
1934
1935=back
1936
1937=head1 Configuration and Compilation
1938
1939=over 4
1940
1941=item *
1942
1943Added C<useversionedarchname> option to Configure
1944
1945When set, it includes 'api_versionstring' in 'archname'. E.g.
1946x86_64-linux-5.13.6-thread-multi. It is unset by default.
1947
1948This feature was requested by Tim Bunce, who observed that
f105b7be 1949C<INSTALL_BASE> creates a library structure that does not
5ed58cbd
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1950differentiate by perl version. Instead, it places architecture
1951specific files in "$install_base/lib/perl5/$archname". This makes
f105b7be 1952it difficult to use a common C<INSTALL_BASE> library path with
5ed58cbd
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1953multiple versions of perl.
1954
f105b7be 1955By setting C<-Duseversionedarchname>, the $archname will be
c2959982 1956distinct for architecture I<and> API version, allowing mixed use of
f105b7be 1957C<INSTALL_BASE>.
5ed58cbd
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1958
1959=item *
1960
ff772877
RS
1961Add a C<PERL_NO_INLINE_FUNCTIONS> option
1962
f105b7be 1963If C<PERL_NO_INLINE_FUNCTIONS> is defined, don't include "inline.h"
ff772877
RS
1964
1965This permits test code to include the perl headers for definitions without
1966creating a link dependency on the perl library (which may not exist yet).
1967
1968=item *
1969
5ed58cbd
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1970Configure will honour the external C<MAILDOMAIN> environment variable, if set.
1971
1972=item *
1973
1974C<installman> no longer ignores the silent option
1975
1976=item *
1977
1978Both C<META.yml> and C<META.json> files are now included in the distribution.
1979
1980=item *
1981
1982F<Configure> will now correctly detect C<isblank()> when compiling with a C++
1983compiler.
1984
1985=item *
1986
1987The pager detection in F<Configure> has been improved to allow responses which
1988specify options after the program name, e.g. B</usr/bin/less -R>, if the user
1989accepts the default value. This helps B<perldoc> when handling ANSI escapes
1990[perl #72156].
1991
1992=back
1993
1994=head1 Testing
1995
1996=over 4
1997
1998=item *
1999
2000The test suite now has a section for tests that require very large amounts
2001of memory. These tests won't run by default; they can be enabled by
2002setting the C<PERL_TEST_MEMORY> environment variable to the number of
2003gibibytes of memory that may be safely used.
2004
2005=back
2006
2007=head1 Platform Support
2008
2009=head2 Discontinued Platforms
2010
2011=over 4
2012
2013=item BeOS
2014
2015BeOS was an operating system for personal computers developed by Be Inc,
2016initially for their BeBox hardware. The OS Haiku was written as an open
2017source replacement for/continuation of BeOS, and its perl port is current and
2018actively maintained.
2019
2020=item UTS Global
2021
2022Support code relating to UTS global has been removed. UTS was a mainframe
2023version of System V created by Amdahl, subsequently sold to UTS Global. The
e612b5a0 2024port has not been touched since before Perl v5.8.0, and UTS Global is now
5ed58cbd
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2025defunct.
2026
2027=item VM/ESA
2028
2029Support for VM/ESA has been removed. The port was tested on 2.3.0, which
2030IBM ended service on in March 2002. 2.4.0 ended service in June 2003, and
2031was superseded by Z/VM. The current version of Z/VM is V6.2.0, and scheduled
2032for end of service on 2015/04/30.
2033
2034=item MPE/IX
2035
2036Support for MPE/IX has been removed.
2037
2038=item EPOC
2039
2040Support code relating to EPOC has been removed. EPOC was a family of
2041operating systems developed by Psion for mobile devices. It was the
2042predecessor of Symbian. The port was last updated in April 2002.
2043
2044=item Rhapsody
2045
2046Support for Rhapsody has been removed.
2047
2048=back
2049
2050=head2 Platform-Specific Notes
2051
2052=head3 AIX
2053
2054Configure now always adds C<-qlanglvl=extc99> to the CC flags on AIX when
2055using xlC. This will make it easier to compile a number of XS-based modules
2056that assume C99 [perl #113778].
2057
2058=head3 clang++
2059
2060There is now a workaround for a compiler bug that prevented compiling
e612b5a0 2061with clang++ since Perl v5.15.7 [perl #112786].
5ed58cbd
RS
2062
2063=head3 C++
2064
2065When compiling the Perl core as C++ (which is only semi-supported), the
2066mathom functions are now compiled as C<extern "C">, to ensure proper
2067binary compatibility. (However, binary compatibility isn't generally
2068guaranteed anyway in the situations where this would matter.)
2069
2070=head3 Darwin
2071
2072Stop hardcoding an alignment on 8 byte boundaries to fix builds using
2073-Dusemorebits.
2074
2075=head3 Haiku
2076
2077Perl should now work out of the box on Haiku R1 Alpha 4.
2078
2079=head3 MidnightBSD
2080
2081C<libc_r> was removed from recent versions of MidnightBSD and older versions
2082work better with C<pthread>. Threading is now enabled using C<pthread> which
2083corrects build errors with threading enabled on 0.4-CURRENT.
2084
2085=head3 Solaris
2086
2087In Configure, avoid running sed commands with flags not supported on Solaris.
2088
2089=head3 VMS
2090
2091=over
2092
2093=item *
2094
2095Where possible, the case of filenames and command-line arguments is now
2096preserved by enabling the CRTL features C<DECC$EFS_CASE_PRESERVE> and
2097C<DECC$ARGV_PARSE_STYLE> at start-up time. The latter only takes effect
2098when extended parse is enabled in the process from which Perl is run.
2099
2100=item *
2101
2102The character set for Extended Filename Syntax (EFS) is now enabled by default
2103on VMS. Among other things, this provides better handling of dots in directory
05f5908f 2104names, multiple dots in filenames, and spaces in filenames. To obtain the old
5ed58cbd
RS
2105behavior, set the logical name C<DECC$EFS_CHARSET> to C<DISABLE>.
2106
2107=item *
2108
05f5908f 2109Fixed linking on builds configured with C<-Dusemymalloc=y>.
5ed58cbd
RS
2110
2111=item *
2112
05f5908f
CB
2113Experimental support for building Perl with the HP C++ compiler is available
2114by configuring with C<-Dusecxx>.
5ed58cbd
RS
2115
2116=item *
2117
2118All C header files from the top-level directory of the distribution are now
2119installed on VMS, providing consistency with a long-standing practice on other
2120platforms. Previously only a subset were installed, which broke non-core
2121extension builds for extensions that depended on the missing include files.
2122
2123=item *
2124
2125Quotes are now removed from the command verb (but not the parameters) for
2126commands spawned via C<system>, backticks, or a piped C<open>. Previously,
2127quotes on the verb were passed through to DCL, which would fail to recognize
2128the command. Also, if the verb is actually a path to an image or command
2129procedure on an ODS-5 volume, quoting it now allows the path to contain spaces.
2130
2131=item *
2132
2133The B<a2p> build has been fixed for the HP C++ compiler on OpenVMS.
2134
2135=back
2136
2137=head3 Win32
2138
2139=over
2140
2141=item *
2142
2143Perl can now be built using Microsoft's Visual C++ 2012 compiler by specifying
2144CCTYPE=MSVC110 (or MSVC110FREE if you are using the free Express edition for
2145Windows Desktop) in F<win32/Makefile>.
2146
2147=item *
2148
f105b7be 2149The option to build without C<USE_SOCKETS_AS_HANDLES> has been removed.
5ed58cbd
RS
2150
2151=item *
2152
2153Fixed a problem where perl could crash while cleaning up threads (including the
2154main thread) in threaded debugging builds on Win32 and possibly other platforms
2155[perl #114496].
2156
2157=item *
2158
2159A rare race condition that would lead to L<sleep|perlfunc/sleep> taking more
2160time than requested, and possibly even hanging, has been fixed [perl #33096].
2161
2162=item *
2163
2164C<link> on Win32 now attempts to set C<$!> to more appropriate values
2165based on the Win32 API error code. [perl #112272]
2166
2167Perl no longer mangles the environment block, e.g. when launching a new
2168sub-process, when the environment contains non-ASCII characters. Known
2169problems still remain, however, when the environment contains characters
2170outside of the current ANSI codepage (e.g. see the item about Unicode in
2171C<%ENV> in L<http://perl5.git.perl.org/perl.git/blob/HEAD:/Porting/todo.pod>).
2172[perl #113536]
2173
2174=item *
2175
2176Building perl with some Windows compilers used to fail due to a problem
2177with miniperl's C<glob> operator (which uses the C<perlglob> program)
2178deleting the PATH environment variable [perl #113798].
2179
2180=item *
2181
f105b7be 2182A new makefile option, C<USE_64_BIT_INT>, has been added to the Windows
5ed58cbd
RS
2183makefiles. Set this to "define" when building a 32-bit perl if you want
2184it to use 64-bit integers.
2185
2186Machine code size reductions, already made to the DLLs of XS modules in
e612b5a0 2187Perl v5.17.2, have now been extended to the perl DLL itself.
5ed58cbd 2188
e612b5a0 2189Building with VC++ 6.0 was inadvertently broken in Perl v5.17.2 but has
5ed58cbd
RS
2190now been fixed again.
2191
2192=back
2193
2194=head3 WinCE
2195
2196Building on WinCE is now possible once again, although more work is required
2197to fully restore a clean build.
2198
2199=head1 Internal Changes
2200
2201=over
2202
2203=item *
2204
4263dd11 2205Synonyms for the misleadingly named C<av_len()> have been created:
5ed58cbd
RS
2206C<av_top_index()> and C<av_tindex>. All three of these return the
2207number of the highest index in the array, not the number of elements it
2208contains.
2209
2210=item *
2211
2212SvUPGRADE() is no longer an expression. Originally this macro (and its
2213underlying function, sv_upgrade()) were documented as boolean, although
2214in reality they always croaked on error and never returned false. In 2005
2215the documentation was updated to specify a void return value, but
2216SvUPGRADE() was left always returning 1 for backwards compatibility. This
2217has now been removed, and SvUPGRADE() is now a statement with no return
2218value.
2219
2220So this is now a syntax error:
2221
2222 if (!SvUPGRADE(sv)) { croak(...); }
2223
2224If you have code like that, simply replace it with
2225
2226 SvUPGRADE(sv);
2227
237b9c6d 2228or to avoid compiler warnings with older perls, possibly
5ed58cbd
RS
2229
2230 (void)SvUPGRADE(sv);
2231
2232=item *
2233
2234Perl has a new copy-on-write mechanism that allows any SvPOK scalar to be
2235upgraded to a copy-on-write scalar. A reference count on the string buffer
d16360cf
RS
2236is stored in the string buffer itself. This feature is B<not enabled by
2237default>.
5ed58cbd 2238
d16360cf
RS
2239It can be enabled in a perl build by running F<Configure> with
2240B<-Accflags=-DPERL_NEW_COPY_ON_WRITE>, and we would encourage XS authors
2241to try their code with such an enabled perl, and provide feedback.
2242Unfortunately, there is not yet a good guide to updating XS code to cope
2243with COW. Until such a document is available, consult the perl5-porters
2244mailing list.
5ed58cbd 2245
d16360cf
RS
2246It breaks a few XS modules by allowing copy-on-write scalars to go
2247through code paths that never encountered them before.
5ed58cbd
RS
2248
2249=item *
2250
2251Copy-on-write no longer uses the SvFAKE and SvREADONLY flags. Hence,
2252SvREADONLY indicates a true read-only SV.
2253
2254Use the SvIsCOW macro (as before) to identify a copy-on-write scalar.
2255
2256=item *
2257
f105b7be 2258C<PL_glob_index> is gone.
5ed58cbd
RS
2259
2260=item *
2261
2262The private Perl_croak_no_modify has had its context parameter removed. It is
2263now has a void prototype. Users of the public API croak_no_modify remain
2264unaffected.
2265
2266=item *
2267
2268Copy-on-write (shared hash key) scalars are no longer marked read-only.
2269C<SvREADONLY> returns false on such an SV, but C<SvIsCOW> still returns
2270true.
2271
2272=item *
2273
2274A new op type, C<OP_PADRANGE> has been introduced. The perl peephole
2275optimiser will, where possible, substitute a single padrange op for a
2276pushmark followed by one or more pad ops, and possibly also skipping list
2277and nextstate ops. In addition, the op can carry out the tasks associated
f105b7be 2278with the RHS of a C<< my(...) = @_ >> assignment, so those ops may be optimised
5ed58cbd
RS
2279away too.
2280
2281=item *
2282
2283Case-insensitive matching inside a [bracketed] character class with a
2284multi-character fold no longer excludes one of the possibilities in the
2285circumstances that it used to. [perl #89774].
2286
2287=item *
2288
2289C<PL_formfeed> has been removed.
2290
2291=item *
2292
2293The regular expression engine no longer reads one byte past the end of the
2294target string. While for all internally well-formed scalars this should
2295never have been a problem, this change facilitates clever tricks with
2296string buffers in CPAN modules. [perl #73542]
2297
2298=item *
2299
2300Inside a BEGIN block, C<PL_compcv> now points to the currently-compiling
2301subroutine, rather than the BEGIN block itself.
2302
2303=item *
2304
2305C<mg_length> has been deprecated.
2306
2307=item *
2308
2309C<sv_len> now always returns a byte count and C<sv_len_utf8> a character
2310count. Previously, C<sv_len> and C<sv_len_utf8> were both buggy and would
2311sometimes returns bytes and sometimes characters. C<sv_len_utf8> no longer
be12dd22 2312assumes that its argument is in UTF-8. Neither of these creates UTF-8 caches
5ed58cbd
RS
2313for tied or overloaded values or for non-PVs any more.
2314
2315=item *
2316
2317C<sv_mortalcopy> now copies string buffers of shared hash key scalars when
2318called from XS modules [perl #79824].
2319
2320=item *
2321
2322C<RXf_SPLIT> and C<RXf_SKIPWHITE> are no longer used. They are now
2323#defined as 0.
2324
2325=item *
2326
2327The new C<RXf_MODIFIES_VARS> flag can be set by custom regular expression
2328engines to indicate that the execution of the regular expression may cause
2329variables to be modified. This lets C<s///> know to skip certain
2330optimisations. Perl's own regular expression engine sets this flag for the
2331special backtracking verbs that set $REGMARK and $REGERROR.
2332
2333=item *
2334
2335The APIs for accessing lexical pads have changed considerably.
2336
2337C<PADLIST>s are now longer C<AV>s, but their own type instead.
2338C<PADLIST>s now contain a C<PAD> and a C<PADNAMELIST> of C<PADNAME>s,
2339rather than C<AV>s for the pad and the list of pad names. C<PAD>s,
2340C<PADNAMELIST>s, and C<PADNAME>s are to be accessed as such through the
2341newly added pad API instead of the plain C<AV> and C<SV> APIs. See
2342L<perlapi> for details.
2343
2344=item *
2345
2346In the regex API, the numbered capture callbacks are passed an index
2347indicating what match variable is being accessed. There are special
2348index values for the C<$`, $&, $&> variables. Previously the same three
2349values were used to retrieve C<${^PREMATCH}, ${^MATCH}, ${^POSTMATCH}>
2350too, but these have now been assigned three separate values. See
2351L<perlreapi/Numbered capture callbacks>.
2352
2353=item *
2354
2355C<PL_sawampersand> was previously a boolean indicating that any of
2356C<$`, $&, $&> had been seen; it now contains three one-bit flags
2357indicating the presence of each of the variables individually.
2358
2359=item *
2360
2361The C<CV *> typemap entry now supports C<&{}> overloading and typeglobs,
2362just like C<&{...}> [perl #96872].
2363
2364=item *
2365
2366The C<SVf_AMAGIC> flag to indicate overloading is now on the stash, not the
2367object. It is now set automatically whenever a method or @ISA changes, so
2368its meaning has changed, too. It now means "potentially overloaded". When
2369the overload table is calculated, the flag is automatically turned off if
2370there is no overloading, so there should be no noticeable slowdown.
2371
2372The staleness of the overload tables is now checked when overload methods
2373are invoked, rather than during C<bless>.
2374
2375"A" magic is gone. The changes to the handling of the C<SVf_AMAGIC> flag
2376eliminate the need for it.
2377
2378C<PL_amagic_generation> has been removed as no longer necessary. For XS
2379modules, it is now a macro alias to C<PL_na>.
2380
2381The fallback overload setting is now stored in a stash entry separate from
2382overloadedness itself.
2383
2384=item *
2385
2386The character-processing code has been cleaned up in places. The changes
2387should be operationally invisible.
2388
2389=item *
2390
e612b5a0 2391The C<study> function was made a no-op in v5.16. It was simply disabled via
5ed58cbd
RS
2392a C<return> statement; the code was left in place. Now the code supporting
2393what C<study> used to do has been removed.
2394
2395=item *
2396
2397Under threaded perls, there is no longer a separate PV allocated for every
2398COP to store its package name (C<< cop->stashpv >>). Instead, there is an
2399offset (C<< cop->stashoff >>) into the new C<PL_stashpad> array, which
2400holds stash pointers.
2401
2402=item *
2403
2404In the pluggable regex API, the C<regexp_engine> struct has acquired a new
2405field C<op_comp>, which is currently just for perl's internal use, and
f105b7be 2406should be initialized to NULL by other regex plugin modules.
5ed58cbd
RS
2407
2408=item *
2409
7779650e 2410A new function C<alloccopstash> has been added to the API, but is considered
5ed58cbd
RS
2411experimental. See L<perlapi>.
2412
2413=item *
2414
2415Perl used to implement get magic in a way that would sometimes hide bugs in
4263dd11 2416code that could call mg_get() too many times on magical values. This hiding of
5ed58cbd
RS
2417errors no longer occurs, so long-standing bugs may become visible now. If
2418you see magic-related errors in XS code, check to make sure it, together
2419with the Perl API functions it uses, calls mg_get() only once on SvGMAGICAL()
2420values.
2421
2422=item *
2423
2424OP allocation for CVs now uses a slab allocator. This simplifies
2425memory management for OPs allocated to a CV, so cleaning up after a
2426compilation error is simpler and safer [perl #111462][perl #112312].
2427
2428=item *
2429
f105b7be 2430C<PERL_DEBUG_READONLY_OPS> has been rewritten to work with the new slab
5ed58cbd
RS
2431allocator, allowing it to catch more violations than before.
2432
2433=item *
2434
f105b7be
KE
2435The old slab allocator for ops, which was only enabled for C<PERL_IMPLICIT_SYS>
2436and C<PERL_DEBUG_READONLY_OPS>, has been retired.
5ed58cbd
RS
2437
2438=back
2439
2440=head1 Selected Bug Fixes
2441
2442=over 4
2443
2444=item *
2445
2446Here-doc terminators no longer require a terminating newline character when
2447they occur at the end of a file. This was already the case at the end of a
2448string eval [perl #65838].
2449
2450=item *
2451
f105b7be 2452C<-DPERL_GLOBAL_STRUCT> builds now free the global struct B<after>
5ed58cbd
RS
2453they've finished using it.
2454
2455=item *
2456
2457A trailing '/' on a path in @INC will no longer have an additional '/'
2458appended.
2459
2460=item *
2461
2462The C<:crlf> layer now works when unread data doesn't fit into its own
2463buffer. [perl #112244].
2464
2465=item *
2466
2467C<ungetc()> now handles UTF-8 encoded data. [perl #116322].
2468
2469=item *
2470
2471A bug in the core typemap caused any C types that map to the T_BOOL core
2472typemap entry to not be set, updated, or modified when the T_BOOL variable was
2473used in an OUTPUT: section with an exception for RETVAL. T_BOOL in an INPUT:
2474section was not affected. Using a T_BOOL return type for an XSUB (RETVAL)
2475was not affected. A side effect of fixing this bug is, if a T_BOOL is specified
2476in the OUTPUT: section (which previous did nothing to the SV), and a read only
2477SV (literal) is passed to the XSUB, croaks like "Modification of a read-only
2478value attempted" will happen. [perl #115796]
2479
2480=item *
2481
2482On many platforms, providing a directory name as the script name caused perl
2483to do nothing and report success. It should now universally report an error
2484and exit nonzero. [perl #61362]
2485
2486=item *
2487
2488C<sort {undef} ...> under fatal warnings no longer crashes. It had
e612b5a0 2489begun crashing in Perl v5.16.
5ed58cbd
RS
2490
2491=item *
2492
2493Stashes blessed into each other
2494(C<bless \%Foo::, 'Bar'; bless \%Bar::, 'Foo'>) no longer result in double
e612b5a0 2495frees. This bug started happening in Perl v5.16.
5ed58cbd
RS
2496
2497=item *
2498
2499Numerous memory leaks have been fixed, mostly involving fatal warnings and
2500syntax errors.
2501
2502=item *
2503
2504Some failed regular expression matches such as C<'f' =~ /../g> were not
2505resetting C<pos>. Also, "match-once" patterns (C<m?...?g>) failed to reset
2506it, too, when invoked a second time [perl #23180].
2507
2508=item *
2509
5ed58cbd
RS
2510Several bugs involving C<local *ISA> and C<local *Foo::> causing stale
2511MRO caches have been fixed.
2512
2513=item *
2514
2515Defining a subroutine when its typeglob has been aliased no longer results
e612b5a0 2516in stale method caches. This bug was introduced in Perl v5.10.
5ed58cbd
RS
2517
2518=item *
2519
2520Localising a typeglob containing a subroutine when the typeglob's package
2521has been deleted from its parent stash no longer produces an error. This
e612b5a0 2522bug was introduced in Perl v5.14.
5ed58cbd
RS
2523
2524=item *
2525
2526Under some circumstances, C<local *method=...> would fail to reset method
2527caches upon scope exit.
2528
2529=item *
2530
2531C</[.foo.]/> is no longer an error, but produces a warning (as before) and
2532is treated as C</[.fo]/> [perl #115818].
2533
2534=item *
2535
2536C<goto $tied_var> now calls FETCH before deciding what type of goto
2537(subroutine or label) this is.
2538
2539=item *
2540
2541Renaming packages through glob assignment
2542(C<*Foo:: = *Bar::; *Bar:: = *Baz::>) in combination with C<m?...?> and
2543C<reset> no longer makes threaded builds crash.
2544
2545=item *
2546
2547A number of bugs related to assigning a list to hash have been fixed. Many of
2548these involve lists with repeated keys like C<(1, 1, 1, 1)>.
2549
2550=over 4
2551
2552=item *
2553
2554The expression C<scalar(%h = (1, 1, 1, 1))> now returns C<4>, not C<2>.
2555
2556=item *
2557
2558The return value of C<%h = (1, 1, 1)> in list context was wrong. Previously
2559this would return C<(1, undef, 1)>, now it returns C<(1, undef)>.
2560
2561=item *
2562
2563Perl now issues the same warning on C<($s, %h) = (1, {})> as it does for
2564C<(%h) = ({})>, "Reference found where even-sized list expected".
2565
2566=item *
2567
2568A number of additional edge cases in list assignment to hashes were
2569corrected. For more details see commit 23b7025ebc.
2570
2571=back
2572
2573=item *
2574
2575Attributes applied to lexical variables no longer leak memory.
2576[perl #114764]
2577
2578=item *
2579
2580C<dump>, C<goto>, C<last>, C<next>, C<redo> or C<require> followed by a
2581bareword (or version) and then an infix operator is no longer a syntax
2582error. It used to be for those infix operators (like C<+>) that have a
2583different meaning where a term is expected. [perl #105924]
2584
2585=item *
2586
2587C<require a::b . 1> and C<require a::b + 1> no longer produce erroneous
2588ambiguity warnings. [perl #107002]
2589
2590=item *
2591
2592Class method calls are now allowed on any string, and not just strings
2593beginning with an alphanumeric character. [perl #105922]
2594
2595=item *
2596
2597An empty pattern created with C<qr//> used in C<m///> no longer triggers
2598the "empty pattern reuses last pattern" behaviour. [perl #96230]
2599
2600=item *
2601
2602Tying a hash during iteration no longer results in a memory leak.
2603
2604=item *
2605
2606Freeing a tied hash during iteration no longer results in a memory leak.
2607
2608=item *
2609
2610List assignment to a tied array or hash that dies on STORE no longer
2611results in a memory leak.
2612
2613=item *
2614
2615If the hint hash (C<%^H>) is tied, compile-time scope entry (which copies
2616the hint hash) no longer leaks memory if FETCH dies. [perl #107000]
2617
2618=item *
2619
2620Constant folding no longer inappropriately triggers the special
2621C<split " "> behaviour. [perl #94490]
2622
2623=item *
2624
2625C<defined scalar(@array)>, C<defined do { &foo }>, and similar constructs
2626now treat the argument to C<defined> as a simple scalar. [perl #97466]
2627
2628=item *
2629
2630Running a custom debugging that defines no C<*DB::DB> glob or provides a
2631subroutine stub for C<&DB::DB> no longer results in a crash, but an error
2632instead. [perl #114990]
2633
2634=item *
2635
2636C<reset ""> now matches its documentation. C<reset> only resets C<m?...?>
2637patterns when called with no argument. An empty string for an argument now
2638does nothing. (It used to be treated as no argument.) [perl #97958]
2639
2640=item *
2641
2642C<printf> with an argument returning an empty list no longer reads past the
2643end of the stack, resulting in erratic behaviour. [perl #77094]
2644
2645=item *
2646
2647C<--subname> no longer produces erroneous ambiguity warnings.
2648[perl #77240]
2649
2650=item *
2651
2652C<v10> is now allowed as a label or package name. This was inadvertently
e612b5a0 2653broken when v-strings were added in Perl v5.6. [perl #56880]
5ed58cbd
RS
2654
2655=item *
2656
2657C<length>, C<pos>, C<substr> and C<sprintf> could be confused by ties,
2658overloading, references and typeglobs if the stringification of such
be12dd22 2659changed the internal representation to or from UTF-8. [perl #114410]
5ed58cbd
RS
2660
2661=item *
2662
2663utf8::encode now calls FETCH and STORE on tied variables. utf8::decode now
2664calls STORE (it was already calling FETCH).
2665
2666=item *
2667
2668C<$tied =~ s/$non_utf8/$utf8/> no longer loops infinitely if the tied
2669variable returns a Latin-1 string, shared hash key scalar, or reference or
2ae351f8 2670typeglob that stringifies as ASCII or Latin-1. This was a regression from
e612b5a0 2671v5.12.
5ed58cbd
RS
2672
2673=item *
2674
2675C<s///> without /e is now better at detecting when it needs to forego
2676certain optimisations, fixing some buggy cases:
2677
2678=over
2679
2680=item *
2681
2682Match variables in certain constructs (C<&&>, C<||>, C<..> and others) in
2683the replacement part; e.g., C<s/(.)/$l{$a||$1}/g>. [perl #26986]
2684
2685=item *
2686
2687Aliases to match variables in the replacement.
2688
2689=item *
2690
2691C<$REGERROR> or C<$REGMARK> in the replacement. [perl #49190]
2692
2693=item *
2694
2695An empty pattern (C<s//$foo/>) that causes the last-successful pattern to
2696be used, when that pattern contains code blocks that modify the variables
2697in the replacement.
2698
2699=back
2700
2701=item *
2702
2703The taintedness of the replacement string no longer affects the taintedness
2704of the return value of C<s///e>.
2705
2706=item *
2707
2708The C<$|> autoflush variable is created on-the-fly when needed. If this
2709happened (e.g., if it was mentioned in a module or eval) when the
2710currently-selected filehandle was a typeglob with an empty IO slot, it used
2711to crash. [perl #115206]
2712
2713=item *
2714
2715Line numbers at the end of a string eval are no longer off by one.
2716[perl #114658]
2717
2718=item *
2719
2720@INC filters (subroutines returned by subroutines in @INC) that set $_ to a
2721copy-on-write scalar no longer cause the parser to modify that string
2722buffer in place.
2723
2724=item *
2725
2726C<length($object)> no longer returns the undefined value if the object has
2727string overloading that returns undef. [perl #115260]
2728
2729=item *
2730
2731The use of C<PL_stashcache>, the stash name lookup cache for method calls, has
2732been restored,
2733
2734Commit da6b625f78f5f133 in August 2011 inadvertently broke the code that looks
2735up values in C<PL_stashcache>. As it's a only cache, quite correctly everything
2736carried on working without it.
2737
2738=item *
2739
e612b5a0 2740The error "Can't localize through a reference" had disappeared in v5.16.0
5ed58cbd 2741when C<local %$ref> appeared on the last line of an lvalue subroutine.
e612b5a0 2742This error disappeared for C<\local %$ref> in perl v5.8.1. It has now
5ed58cbd
RS
2743been restored.
2744
2745=item *
2746
2747The parsing of here-docs has been improved significantly, fixing several
2748parsing bugs and crashes and one memory leak, and correcting wrong
2749subsequent line numbers under certain conditions.
2750
2751=item *
2752
2753Inside an eval, the error message for an unterminated here-doc no longer
2754has a newline in the middle of it [perl #70836].
2755
2756=item *
2757
2758A substitution inside a substitution pattern (C<s/${s|||}//>) no longer
2759confuses the parser.
2760
2761=item *
2762
2763It may be an odd place to allow comments, but C<s//"" # hello/e> has
2764always worked, I<unless> there happens to be a null character before the
2765first #. Now it works even in the presence of nulls.
2766
2767=item *
2768
2769An invalid range in C<tr///> or C<y///> no longer results in a memory leak.
2770
2771=item *
2772
2773String eval no longer treats a semicolon-delimited quote-like operator at
2774the very end (C<eval 'q;;'>) as a syntax error.
2775
2776=item *
2777
2778C<< warn {$_ => 1} + 1 >> is no longer a syntax error. The parser used to
2779get confused with certain list operators followed by an anonymous hash and
2780then an infix operator that shares its form with a unary operator.
2781
2782=item *
2783
2784C<(caller $n)[6]> (which gives the text of the eval) used to return the
2785actual parser buffer. Modifying it could result in crashes. Now it always
2786returns a copy. The string returned no longer has "\n;" tacked on to the
2787end. The returned text also includes here-doc bodies, which used to be
2788omitted.
2789
2790=item *
2791
5cd341ec
RS
2792The UTF-8 position cache is now reset when accessing magical variables, to
2793avoid the string buffer and the UTF-8 position cache getting out of sync
5ed58cbd
RS
2794[perl #114410].
2795
2796=item *
2797
be12dd22
RS
2798Various cases of get magic being called twice for magical UTF-8
2799strings have been fixed.
5ed58cbd
RS
2800
2801=item *
2802
2803This code (when not in the presence of C<$&> etc)
2804
2805 $_ = 'x' x 1_000_000;
2806 1 while /(.)/;
2807
2808used to skip the buffer copy for performance reasons, but suffered from C<$1>
2809etc changing if the original string changed. That's now been fixed.
2810
2811=item *
2812
2813Perl doesn't use PerlIO anymore to report out of memory messages, as PerlIO
2814might attempt to allocate more memory.
2815
2816=item *
2817
2818In a regular expression, if something is quantified with C<{n,m}> where
2819C<S<n E<gt> m>>, it can't possibly match. Previously this was a fatal
2820error, but now is merely a warning (and that something won't match).
2821[perl #82954].
2822
2823=item *
2824
2825It used to be possible for formats defined in subroutines that have
2826subsequently been undefined and redefined to close over variables in the
2827wrong pad (the newly-defined enclosing sub), resulting in crashes or
2828"Bizarre copy" errors.
2829
2830=item *
2831
2832Redefinition of XSUBs at run time could produce warnings with the wrong
2833line number.
2834
2835=item *
2836
2837The %vd sprintf format does not support version objects for alpha versions.
2838It used to output the format itself (%vd) when passed an alpha version, and
2839also emit an "Invalid conversion in printf" warning. It no longer does,
2840but produces the empty string in the output. It also no longer leaks
2841memory in this case.
2842
2843=item *
2844
2845C<< $obj->SUPER::method >> calls in the main package could fail if the
2846SUPER package had already been accessed by other means.
2847
2848=item *
2849
f105b7be 2850Stash aliasing (C<< *foo:: = *bar:: >>) no longer causes SUPER calls to ignore
5ed58cbd
RS
2851changes to methods or @ISA or use the wrong package.
2852
2853=item *
2854
2855Method calls on packages whose names end in ::SUPER are no longer treated
2856as SUPER method calls, resulting in failure to find the method.
2857Furthermore, defining subroutines in such packages no longer causes them to
2858be found by SUPER method calls on the containing package [perl #114924].
2859
2860=item *
2861
2862C<\w> now matches the code points U+200C (ZERO WIDTH NON-JOINER) and U+200D
2863(ZERO WIDTH JOINER). C<\W> no longer matches these. This change is because
2864Unicode corrected their definition of what C<\w> should match.
2865
2866=item *
2867
2868C<dump LABEL> no longer leaks its label.
2869
2870=item *
2871
2872Constant folding no longer changes the behaviour of functions like C<stat()>
2873and C<truncate()> that can take either filenames or handles.
2874C<stat 1 ? foo : bar> nows treats its argument as a file name (since it is an
2875arbitrary expression), rather than the handle "foo".
2876
2877=item *
2878
2879C<truncate FOO, $len> no longer falls back to treating "FOO" as a file name if
e612b5a0 2880the filehandle has been deleted. This was broken in Perl v5.16.0.
5ed58cbd
RS
2881
2882=item *
2883
2884Subroutine redefinitions after sub-to-glob and glob-to-glob assignments no
2885longer cause double frees or panic messages.
2886
2887=item *
2888
2889C<s///> now turns vstrings into plain strings when performing a substitution,
2890even if the resulting string is the same (C<s/a/a/>).
2891
2892=item *
2893
2894Prototype mismatch warnings no longer erroneously treat constant subs as having
2895no prototype when they actually have "".
2896
2897=item *
2898
2899Constant subroutines and forward declarations no longer prevent prototype
2900mismatch warnings from omitting the sub name.
2901
2902=item *
2903
2904C<undef> on a subroutine now clears call checkers.
2905
2906=item *
2907
e612b5a0 2908The C<ref> operator started leaking memory on blessed objects in Perl v5.16.0.
5ed58cbd
RS
2909This has been fixed [perl #114340].
2910
2911=item *
2912
2913C<use> no longer tries to parse its arguments as a statement, making
2914C<use constant { () };> a syntax error [perl #114222].
2915
2916=item *
2917
2918On debugging builds, "uninitialized" warnings inside formats no longer cause
2919assertion failures.
2920
2921=item *
2922
2923On debugging builds, subroutines nested inside formats no longer cause
2924assertion failures [perl #78550].
2925
2926=item *
2927
2928Formats and C<use> statements are now permitted inside formats.
2929
2930=item *
2931
2932C<print $x> and C<sub { print $x }-E<gt>()> now always produce the same output.
2933It was possible for the latter to refuse to close over $x if the variable was
2934not active; e.g., if it was defined outside a currently-running named
2935subroutine.
2936
2937=item *
2938
2939Similarly, C<print $x> and C<print eval '$x'> now produce the same output.
2940This also allows "my $x if 0" variables to be seen in the debugger [perl
2941#114018].
2942
2943=item *
2944
2945Formats called recursively no longer stomp on their own lexical variables, but
2946each recursive call has its own set of lexicals.
2947
2948=item *
2949
2950Attempting to free an active format or the handle associated with it no longer
2951results in a crash.
2952
2953=item *
2954
2955Format parsing no longer gets confused by braces, semicolons and low-precedence
2956operators. It used to be possible to use braces as format delimiters (instead
2957of C<=> and C<.>), but only sometimes. Semicolons and low-precedence operators
2958in format argument lines no longer confuse the parser into ignoring the line's
2959return value. In format argument lines, braces can now be used for anonymous
2960hashes, instead of being treated always as C<do> blocks.
2961
2962=item *
2963
2964Formats can now be nested inside code blocks in regular expressions and other
2965quoted constructs (C</(?{...})/> and C<qq/${...}/>) [perl #114040].
2966
2967=item *
2968
2969Formats are no longer created after compilation errors.
2970
2971=item *
2972
2973Under debugging builds, the B<-DA> command line option started crashing in Perl
e612b5a0 2974v5.16.0. It has been fixed [perl #114368].
5ed58cbd
RS
2975
2976=item *
2977
2978A potential deadlock scenario involving the premature termination of a pseudo-
2979forked child in a Windows build with ithreads enabled has been fixed. This
2980resolves the common problem of the F<t/op/fork.t> test hanging on Windows [perl
2981#88840].
2982
2983=item *
2984
5ed58cbd
RS
2985The code which generates errors from C<require()> could potentially read one or
2986two bytes before the start of the filename for filenames less than three bytes
2987long and ending C</\.p?\z/>. This has now been fixed. Note that it could
2988never have happened with module names given to C<use()> or C<require()> anyway.
2989
2990=item *
2991
2992The handling of pathnames of modules given to C<require()> has been made
2993thread-safe on VMS.
2994
2995=item *
2996
d85cd26b
RS
2997Non-blocking sockets have been fixed on VMS.
2998
2999=item *
3000
5ed58cbd
RS
3001Pod can now be nested in code inside a quoted construct outside of a string
3002eval. This used to work only within string evals [perl #114040].
3003
3004=item *
3005
3006C<goto ''> now looks for an empty label, producing the "goto must have
3007label" error message, instead of exiting the program [perl #111794].
3008
3009=item *
3010
3011C<goto "\0"> now dies with "Can't find label" instead of "goto must have
3012label".
3013
3014=item *
3015
3016The C function C<hv_store> used to result in crashes when used on C<%^H>
3017[perl #111000].
3018
3019=item *
3020
3021A call checker attached to a closure prototype via C<cv_set_call_checker>
3022is now copied to closures cloned from it. So C<cv_set_call_checker> now
3023works inside an attribute handler for a closure.
3024
3025=item *
3026
3027Writing to C<$^N> used to have no effect. Now it croaks with "Modification
3028of a read-only value" by default, but that can be overridden by a custom
3029regular expression engine, as with C<$1> [perl #112184].
3030
3031=item *
3032
3033C<undef> on a control character glob (C<undef *^H>) no longer emits an
3034erroneous warning about ambiguity [perl #112456].
3035
3036=item *
3037
3038For efficiency's sake, many operators and built-in functions return the
3039same scalar each time. Lvalue subroutines and subroutines in the CORE::
3040namespace were allowing this implementation detail to leak through.
3041C<print &CORE::uc("a"), &CORE::uc("b")> used to print "BB". The same thing
3042would happen with an lvalue subroutine returning the return value of C<uc>.
3043Now the value is copied in such cases.
3044
3045=item *
3046
3047C<method {}> syntax with an empty block or a block returning an empty list
3048used to crash or use some random value left on the stack as its invocant.
3049Now it produces an error.
3050
3051=item *
3052
3053C<vec> now works with extremely large offsets (E<gt>2 GB) [perl #111730].
3054
3055=item *
3056
3057Changes to overload settings now take effect immediately, as do changes to
3058inheritance that affect overloading. They used to take effect only after
3059C<bless>.
3060
3061Objects that were created before a class had any overloading used to remain
3062non-overloaded even if the class gained overloading through C<use overload>
3063or @ISA changes, and even after C<bless>. This has been fixed
3064[perl #112708].
3065
3066=item *
3067
3068Classes with overloading can now inherit fallback values.
3069
3070=item *
3071
3072Overloading was not respecting a fallback value of 0 if there were
3073overloaded objects on both sides of an assignment operator like C<+=>
3074[perl #111856].
3075
3076=item *
3077
3078C<pos> now croaks with hash and array arguments, instead of producing
3079erroneous warnings.
3080
3081=item *
3082
3083C<while(each %h)> now implies C<while(defined($_ = each %h))>, like
3084C<readline> and C<readdir>.
3085
3086=item *
3087
3088Subs in the CORE:: namespace no longer crash after C<undef *_> when called
3089with no argument list (C<&CORE::time> with no parentheses).
3090
3091=item *
3092
3093C<unpack> no longer produces the "'/' must follow a numeric type in unpack"
3094error when it is the data that are at fault [perl #60204].
3095
3096=item *
3097
3098C<join> and C<"@array"> now call FETCH only once on a tied C<$">
3099[perl #8931].
3100
3101=item *
3102
3103Some subroutine calls generated by compiling core ops affected by a
3104C<CORE::GLOBAL> override had op checking performed twice. The checking
3105is always idempotent for pure Perl code, but the double checking can
3106matter when custom call checkers are involved.
3107
3108=item *
3109
3110A race condition used to exist around fork that could cause a signal sent to
3111the parent to be handled by both parent and child. Signals are now blocked
3112briefly around fork to prevent this from happening [perl #82580].
3113
3114=item *
3115
3116The implementation of code blocks in regular expressions, such as C<(?{})>
3117and C<(??{})>, has been heavily reworked to eliminate a whole slew of bugs.
3118The main user-visible changes are:
3119
3120=over 4
3121
3122=item *
3123
3124Code blocks within patterns are now parsed in the same pass as the
3125surrounding code; in particular it is no longer necessary to have balanced
3126braces: this now works:
3127
3128 /(?{ $x='{' })/
3129
3130This means that this error message is no longer generated:
3131
3132 Sequence (?{...}) not terminated or not {}-balanced in regex
3133
3134but a new error may be seen:
3135
3136 Sequence (?{...}) not terminated with ')'
3137
3138In addition, literal code blocks within run-time patterns are only
3139compiled once, at perl compile-time:
3140
3141 for my $p (...) {
3142 # this 'FOO' block of code is compiled once,
3143 # at the same time as the surrounding 'for' loop
3144 /$p{(?{FOO;})/;
3145 }
3146
3147=item *
3148
3149Lexical variables are now sane as regards scope, recursion and closure
3150behavior. In particular, C</A(?{B})C/> behaves (from a closure viewpoint)
3151exactly like C</A/ && do { B } && /C/>, while C<qr/A(?{B})C/> is like
3152C<sub {/A/ && do { B } && /C/}>. So this code now works how you might
3153expect, creating three regexes that match 0, 1, and 2:
3154
3155 for my $i (0..2) {
3156 push @r, qr/^(??{$i})$/;
3157 }
3158 "1" =~ $r[1]; # matches
3159
3160=item *
3161
3162The C<use re 'eval'> pragma is now only required for code blocks defined
3163at runtime; in particular in the following, the text of the C<$r> pattern is
3164still interpolated into the new pattern and recompiled, but the individual
3165compiled code-blocks within C<$r> are reused rather than being recompiled,
3166and C<use re 'eval'> isn't needed any more:
3167
3168 my $r = qr/abc(?{....})def/;
3169 /xyz$r/;
3170
3171=item *
3172
3173Flow control operators no longer crash. Each code block runs in a new
3174dynamic scope, so C<next> etc. will not see
3175any enclosing loops. C<return> returns a value
3176from the code block, not from any enclosing subroutine.
3177
3178=item *
3179
3180Perl normally caches the compilation of run-time patterns, and doesn't
3181recompile if the pattern hasn't changed, but this is now disabled if
3182required for the correct behavior of closures. For example:
3183
3184 my $code = '(??{$x})';
3185 for my $x (1..3) {
3186 # recompile to see fresh value of $x each time
3187 $x =~ /$code/;
3188 }
3189
3190=item *
3191
3192The C</msix> and C<(?msix)> etc. flags are now propagated into the return
3193value from C<(??{})>; this now works:
3194
3195 "AB" =~ /a(??{'b'})/i;
3196
3197=item *
3198
3199Warnings and errors will appear to come from the surrounding code (or for
3200run-time code blocks, from an eval) rather than from an C<re_eval>:
3201
3202 use re 'eval'; $c = '(?{ warn "foo" })'; /$c/;
3203 /(?{ warn "foo" })/;
3204
3205formerly gave:
3206
3207 foo at (re_eval 1) line 1.
3208 foo at (re_eval 2) line 1.
3209
3210and now gives:
3211
3212 foo at (eval 1) line 1.
3213 foo at /some/prog line 2.
3214
3215=back
3216
3217=item *
3218
2e7bc647
KW
3219Perl now can be recompiled to use any Unicode version. In v5.16, it
3220worked on Unicodes 6.0 and 6.1, but there were various bugs if earlier
3221releases were used; the older the release the more problems.
5ed58cbd
RS
3222
3223=item *
3224
3225C<vec> no longer produces "uninitialized" warnings in lvalue context
3226[perl #9423].
3227
3228=item *
3229
3230An optimization involving fixed strings in regular expressions could cause
3231a severe performance penalty in edge cases. This has been fixed
3232[perl #76546].
3233
3234=item *
3235
3236In certain cases, including empty subpatterns within a regular expression (such
3237as C<(?:)> or C<(?:|)>) could disable some optimizations. This has been fixed.
3238
3239=item *
3240
3241The "Can't find an opnumber" message that C<prototype> produces when passed
3242a string like "CORE::nonexistent_keyword" now passes UTF-8 and embedded
3243NULs through unchanged [perl #97478].
3244
3245=item *
3246
3247C<prototype> now treats magical variables like C<$1> the same way as
3248non-magical variables when checking for the CORE:: prefix, instead of
3249treating them as subroutine names.
3250
3251=item *
3252
3253Under threaded perls, a runtime code block in a regular expression could
3254corrupt the package name stored in the op tree, resulting in bad reads
3255in C<caller>, and possibly crashes [perl #113060].
3256
3257=item *
3258
3259Referencing a closure prototype (C<\&{$_[1]}> in an attribute handler for a
3260closure) no longer results in a copy of the subroutine (or assertion
3261failures on debugging builds).
3262
3263=item *
3264
3265C<eval '__PACKAGE__'> now returns the right answer on threaded builds if
3266the current package has been assigned over (as in
3267C<*ThisPackage:: = *ThatPackage::>) [perl #78742].
3268
3269=item *
3270
3271If a package is deleted by code that it calls, it is possible for C<caller>
3272to see a stack frame belonging to that deleted package. C<caller> could
3273crash if the stash's memory address was reused for a scalar and a
3274substitution was performed on the same scalar [perl #113486].
3275
3276=item *
3277
3278C<UNIVERSAL::can> no longer treats its first argument differently
3279depending on whether it is a string or number internally.
3280
3281=item *
3282
3283C<open> with C<< <& >> for the mode checks to see whether the third argument is
3284a number, in determining whether to treat it as a file descriptor or a handle
3285name. Magical variables like C<$1> were always failing the numeric check and
3286being treated as handle names.
3287
3288=item *
3289
3290C<warn>'s handling of magical variables (C<$1>, ties) has undergone several
3291fixes. C<FETCH> is only called once now on a tied argument or a tied C<$@>
3292[perl #97480]. Tied variables returning objects that stringify as "" are
3293no longer ignored. A tied C<$@> that happened to return a reference the
3294I<previous> time it was used is no longer ignored.
3295
3296=item *
3297
3298C<warn ""> now treats C<$@> with a number in it the same way, regardless of
3299whether it happened via C<$@=3> or C<$@="3">. It used to ignore the
3300former. Now it appends "\t...caught", as it has always done with
3301C<$@="3">.
3302
3303=item *
3304
3305Numeric operators on magical variables (e.g., S<C<$1 + 1>>) used to use
3306floating point operations even where integer operations were more appropriate,
3307resulting in loss of accuracy on 64-bit platforms [perl #109542].
3308
3309=item *
3310
3311Unary negation no longer treats a string as a number if the string happened
3312to be used as a number at some point. So, if C<$x> contains the string "dogs",
3313C<-$x> returns "-dogs" even if C<$y=0+$x> has happened at some point.
3314
3315=item *
3316
e612b5a0 3317In Perl v5.14, C<-'-10'> was fixed to return "10", not "+10". But magical
5ed58cbd
RS
3318variables (C<$1>, ties) were not fixed till now [perl #57706].
3319
3320=item *
3321
3322Unary negation now treats strings consistently, regardless of the internal
3323C<UTF8> flag.
3324
3325=item *
3326
3327A regression introduced in Perl v5.16.0 involving
3328C<tr/I<SEARCHLIST>/I<REPLACEMENTLIST>/> has been fixed. Only the first
3329instance is supposed to be meaningful if a character appears more than
3330once in C<I<SEARCHLIST>>. Under some circumstances, the final instance
3331was overriding all earlier ones. [perl #113584]
3332
3333=item *
3334
3335Regular expressions like C<qr/\87/> previously silently inserted a NUL
3336character, thus matching as if it had been written C<qr/\00087/>. Now it
3337matches as if it had been written as C<qr/87/>, with a message that the
3338sequence C<"\8"> is unrecognized.
3339
3340=item *
3341
3342C<__SUB__> now works in special blocks (C<BEGIN>, C<END>, etc.).
3343
3344=item *
3345
3346Thread creation on Windows could theoretically result in a crash if done
3347inside a C<BEGIN> block. It still does not work properly, but it no longer
3348crashes [perl #111610].
3349
3350=item *
3351
3352C<\&{''}> (with the empty string) now autovivifies a stub like any other
3353sub name, and no longer produces the "Unable to create sub" error
3354[perl #94476].
3355
3356=item *
3357
3358A regression introduced in v5.14.0 has been fixed, in which some calls
3359to the C<re> module would clobber C<$_> [perl #113750].
3360
3361=item *
3362
3363C<do FILE> now always either sets or clears C<$@>, even when the file can't be
3364read. This ensures that testing C<$@> first (as recommended by the
3365documentation) always returns the correct result.
3366
3367=item *
3368
3369The array iterator used for the C<each @array> construct is now correctly
237b9c6d
SK
3370reset when C<@array> is cleared [perl #75596]. This happens, for example, when
3371the array is globally assigned to, as in C<@array = (...)>, but not when its
5ed58cbd
RS
3372B<values> are assigned to. In terms of the XS API, it means that C<av_clear()>
3373will now reset the iterator.
3374
3375This mirrors the behaviour of the hash iterator when the hash is cleared.
3376
3377=item *
3378
3379C<< $class->can >>, C<< $class->isa >>, and C<< $class->DOES >> now return
3380correct results, regardless of whether that package referred to by C<$class>
3381exists [perl #47113].
3382
3383=item *
3384
3385Arriving signals no longer clear C<$@> [perl #45173].
3386
3387=item *
3388
3389Allow C<my ()> declarations with an empty variable list [perl #113554].
3390
3391=item *
3392
3393During parsing, subs declared after errors no longer leave stubs
3394[perl #113712].
3395
3396=item *
3397
3398Closures containing no string evals no longer hang on to their containing
3399subroutines, allowing variables closed over by outer subroutines to be
3400freed when the outer sub is freed, even if the inner sub still exists
3401[perl #89544].
3402
3403=item *
3404
3405Duplication of in-memory filehandles by opening with a "<&=" or ">&=" mode
e612b5a0 3406stopped working properly in v5.16.0. It was causing the new handle to
5ed58cbd
RS
3407reference a different scalar variable. This has been fixed [perl #113764].
3408
3409=item *
3410
3411C<qr//> expressions no longer crash with custom regular expression engines
3412that do not set C<offs> at regular expression compilation time
3413[perl #112962].
3414
3415=item *
3416
3417C<delete local> no longer crashes with certain magical arrays and hashes
3418[perl #112966].
3419
3420=item *
3421
3422C<local> on elements of certain magical arrays and hashes used not to
3423arrange to have the element deleted on scope exit, even if the element did
3424not exist before C<local>.
3425
3426=item *
3427
3428C<scalar(write)> no longer returns multiple items [perl #73690].
3429
3430=item *
3431
3432String to floating point conversions no longer misparse certain strings under
3433C<use locale> [perl #109318].
3434
3435=item *
3436
3437C<@INC> filters that die no longer leak memory [perl #92252].
3438
3439=item *
3440
3441The implementations of overloaded operations are now called in the correct
3442context. This allows, among other things, being able to properly override
3443C<< <> >> [perl #47119].
3444
3445=item *
3446
3447Specifying only the C<fallback> key when calling C<use overload> now behaves
3448properly [perl #113010].
3449
3450=item *
3451
3452C<< sub foo { my $a = 0; while ($a) { ... } } >> and
3453C<< sub foo { while (0) { ... } } >> now return the same thing [perl #73618].
3454
3455=item *
3456
3457String negation now behaves the same under C<use integer;> as it does
3458without [perl #113012].
3459
3460=item *
3461
3462C<chr> now returns the Unicode replacement character (U+FFFD) for -1,
3463regardless of the internal representation. -1 used to wrap if the argument
3464was tied or a string internally.
3465
3466=item *
3467
3468Using a C<format> after its enclosing sub was freed could crash as of
e612b5a0 3469perl v5.12.0, if the format referenced lexical variables from the outer sub.
5ed58cbd
RS
3470
3471=item *
3472
3473Using a C<format> after its enclosing sub was undefined could crash as of
e612b5a0 3474perl v5.10.0, if the format referenced lexical variables from the outer sub.
5ed58cbd
RS
3475
3476=item *
3477
3478Using a C<format> defined inside a closure, which format references
3479lexical variables from outside, never really worked unless the C<write>
e612b5a0 3480call was directly inside the closure. In v5.10.0 it even started crashing.
5ed58cbd
RS
3481Now the copy of that closure nearest the top of the call stack is used to
3482find those variables.
3483
3484=item *
3485
3486Formats that close over variables in special blocks no longer crash if a
3487stub exists with the same name as the special block before the special
3488block is compiled.
3489
3490=item *
3491
3492The parser no longer gets confused, treating C<eval foo ()> as a syntax
3493error if preceded by C<print;> [perl #16249].
3494
3495=item *
3496
3497The return value of C<syscall> is no longer truncated on 64-bit platforms
3498[perl #113980].
3499
3500=item *
3501
3502Constant folding no longer causes C<print 1 ? FOO : BAR> to print to the
3503FOO handle [perl #78064].
3504
3505=item *
3506
3507C<do subname> now calls the named subroutine and uses the file name it
3508returns, instead of opening a file named "subname".
3509
3510=item *
3511
3512Subroutines looked up by rv2cv check hooks (registered by XS modules) are
3513now taken into consideration when determining whether C<foo bar> should be
3514the sub call C<foo(bar)> or the method call C<< "bar"->foo >>.
3515
3516=item *
3517
3518C<CORE::foo::bar> is no longer treated specially, allowing global overrides
3519to be called directly via C<CORE::GLOBAL::uc(...)> [perl #113016].
3520
3521=item *
3522
3523Calling an undefined sub whose typeglob has been undefined now produces the
3524customary "Undefined subroutine called" error, instead of "Not a CODE
3525reference".
3526
3527=item *
3528
3529Two bugs involving @ISA have been fixed. C<*ISA = *glob_without_array> and
3530C<undef *ISA; @{*ISA}> would prevent future modifications to @ISA from
3531updating the internal caches used to look up methods. The
e612b5a0 3532*glob_without_array case was a regression from Perl v5.12.
5ed58cbd
RS
3533
3534=item *
3535
3536Regular expression optimisations sometimes caused C<$> with C</m> to
3537produce failed or incorrect matches [perl #114068].
3538
3539=item *
3540
3541C<__SUB__> now works in a C<sort> block when the enclosing subroutine is
3542predeclared with C<sub foo;> syntax [perl #113710].
3543
3544=item *
3545
3546Unicode properties only apply to Unicode code points, which leads to
3547some subtleties when regular expressions are matched against
3548above-Unicode code points. There is a warning generated to draw your
3549attention to this. However, this warning was being generated
3550inappropriately in some cases, such as when a program was being parsed.
3551Non-Unicode matches such as C<\w> and C<[:word;]> should not generate the
3552warning, as their definitions don't limit them to apply to only Unicode
3553code points. Now the message is only generated when matching against
3554C<\p{}> and C<\P{}>. There remains a bug, [perl #114148], for the very
3555few properties in Unicode that match just a single code point. The
3556warning is not generated if they are matched against an above-Unicode
3557code point.
3558
3559=item *
3560
3561Uninitialized warnings mentioning hash elements would only mention the
3562element name if it was not in the first bucket of the hash, due to an
3563off-by-one error.
3564
3565=item *
3566
3567A regular expression optimizer bug could cause multiline "^" to behave
3568incorrectly in the presence of line breaks, such that
3569C<"/\n\n" =~ m#\A(?:^/$)#im> would not match [perl #115242].
3570
3571=item *
3572
3573Failed C<fork> in list context no longer corrupts the stack.
3574C<@a = (1, 2, fork, 3)> used to gobble up the 2 and assign C<(1, undef, 3)>
3575if the C<fork> call failed.
3576
3577=item *
3578
3579Numerous memory leaks have been fixed, mostly involving tied variables that
3580die, regular expression character classes and code blocks, and syntax
3581errors.
3582
3583=item *
3584
3585Assigning a regular expression (C<${qr//}>) to a variable that happens to
3586hold a floating point number no longer causes assertion failures on
3587debugging builds.
3588
3589=item *
3590
3591Assigning a regular expression to a scalar containing a number no longer
f105b7be 3592causes subsequent numification to produce random numbers.
5ed58cbd
RS
3593
3594=item *
3595
3596Assigning a regular expression to a magic variable no longer wipes away the
e612b5a0 3597magic. This was a regression from v5.10.
5ed58cbd
RS
3598
3599=item *
3600
3601Assigning a regular expression to a blessed scalar no longer results in
e612b5a0 3602crashes. This was also a regression from v5.10.
5ed58cbd
RS
3603
3604=item *
3605
3606Regular expression can now be assigned to tied hash and array elements with
3607flattening into strings.
3608
3609=item *
3610
f105b7be 3611Numifying a regular expression no longer results in an uninitialized
5ed58cbd
RS
3612warning.
3613
3614=item *
3615
3616Negative array indices no longer cause EXISTS methods of tied variables to
e612b5a0 3617be ignored. This was a regression from v5.12.
5ed58cbd
RS
3618
3619=item *
3620
3621Negative array indices no longer result in crashes on arrays tied to
3622non-objects.
3623
3624=item *
3625
be12dd22
RS
3626C<$byte_overload .= $utf8> no longer results in doubly-encoded UTF-8 if the
3627left-hand scalar happened to have produced a UTF-8 string the last time
5ed58cbd
RS
3628overloading was invoked.
3629
3630=item *
3631
3632C<goto &sub> now uses the current value of @_, instead of using the array
3633the subroutine was originally called with. This means
3634C<local @_ = (...); goto &sub> now works [perl #43077].
3635
3636=item *
3637
3638If a debugger is invoked recursively, it no longer stomps on its own
3639lexical variables. Formerly under recursion all calls would share the same
3640set of lexical variables [perl #115742].
3641
3642=item *
3643
3644C<*_{ARRAY}> returned from a subroutine no longer spontaneously
3645becomes empty.
3646
3647=back
3648
3649=head1 Known Problems
3650
3651=over 4
3652
3653=item *
3654
7f50b25b 3655There are no known regressions. Please report any bugs you find!
5ed58cbd
RS
3656
3657=back
3658
32b79602
RS
3659=head1 Obituary
3660
3661Hojung Yoon (AMORETTE), 24, of Seoul, South Korea, went to his long rest
3662on May 8, 2013 with llama figurine and autographed TIMTOADY card. He
3663was a brilliant young Perl 5 & 6 hacker and a devoted member of
55c6e7a8 3664Seoul.pm. He programmed Perl, talked Perl, ate Perl, and loved Perl. We
32b79602
RS
3665believe that he is still programming in Perl with his broken IBM laptop
3666somewhere. He will be missed.
3667
5ed58cbd 3668=head1 Acknowledgements
a75569c0 3669
dd38235c
RS
3670Perl v5.18.0 represents approximately 12 months of development since
3671Perl v5.16.0 and contains approximately 400,000 lines of changes across
36722,100 files from 113 authors.
3673
3674Perl continues to flourish into its third decade thanks to a vibrant
3675community of users and developers. The following people are known to
3676have contributed the improvements that became Perl v5.18.0:
3677
3678Aaron Crane, Aaron Trevena, Abhijit Menon-Sen, Adrian M. Enache, Alan
3679Haggai Alavi, Alexandr Ciornii, Andrew Tam, Andy Dougherty, Anton Nikishaev,
3680Aristotle Pagaltzis, Augustina Blair, Bob Ernst, Brad Gilbert, Breno G. de
3681Oliveira, Brian Carlson, Brian Fraser, Charlie Gonzalez, Chip Salzenberg, Chris
3682'BinGOs' Williams, Christian Hansen, Colin Kuskie, Craig A. Berry, Dagfinn
3683Ilmari Mannsåker, Daniel Dragan, Daniel Perrett, Darin McBride, Dave Rolsky,
3684David Golden, David Leadbeater, David Mitchell, David Nicol, Dominic
3685Hargreaves, E. Choroba, Eric Brine, Evan Miller, Father Chrysostomos, Florian
3686Ragwitz, François Perrad, George Greer, Goro Fuji, H.Merijn Brand, Herbert
3687Breunung, Hugo van der Sanden, Igor Zaytsev, James E Keenan, Jan Dubois,
3688Jasmine Ahuja, Jerry D. Hedden, Jess Robinson, Jesse Luehrs, Joaquin Ferrero,
3689Joel Berger, John Goodyear, John Peacock, Karen Etheridge, Karl Williamson,
3690Karthik Rajagopalan, Kent Fredric, Leon Timmermans, Lucas Holt, Lukas Mai,
3691Marcus Holland-Moritz, Markus Jansen, Martin Hasch, Matthew Horsfall, Max
3692Maischein, Michael G Schwern, Michael Schroeder, Moritz Lenz, Nicholas Clark,
3693Niko Tyni, Oleg Nesterov, Patrik Hägglund, Paul Green, Paul Johnson, Paul
3694Marquess, Peter Martini, Rafael Garcia-Suarez, Reini Urban, Renee Baecker,
3695Rhesa Rozendaal, Ricardo Signes, Robin Barker, Ronald J. Kimball, Ruslan
3696Zakirov, Salvador Fandiño, Sawyer X, Scott Lanning, Sergey Alekseev, Shawn M
3697Moore, Shirakata Kentaro, Shlomi Fish, Sisyphus, Smylers, Steffen Müller,
3698Steve Hay, Steve Peters, Steven Schubiger, Sullivan Beck, Sven Strickroth,
3699Sébastien Aperghis-Tramoni, Thomas Sibley, Tobias Leich, Tom Wyant, Tony Cook,
3700Vadim Konovalov, Vincent Pit, Volker Schatz, Walt Mankowski, Yves Orton,
3701Zefram.
3702
3703The list above is almost certainly incomplete as it is automatically generated
3704from version control history. In particular, it does not include the names of
3705the (very much appreciated) contributors who reported issues to the Perl bug
3706tracker.
3707
3708Many of the changes included in this version originated in the CPAN modules
3709included in Perl's core. We're grateful to the entire CPAN community for
3710helping Perl to flourish.
3711
3712For a more complete list of all of Perl's historical contributors, please see
3713the F<AUTHORS> file in the Perl source distribution.
f5b73711 3714
44691e6f
AB
3715=head1 Reporting Bugs
3716
e08634c5
SH
3717If you find what you think is a bug, you might check the articles recently
3718posted to the comp.lang.perl.misc newsgroup and the perl bug database at
3719http://rt.perl.org/perlbug/ . There may also be information at
3720http://www.perl.org/ , the Perl Home Page.
44691e6f 3721
e08634c5
SH
3722If you believe you have an unreported bug, please run the L<perlbug> program
3723included with your release. Be sure to trim your bug down to a tiny but
3724sufficient test case. Your bug report, along with the output of C<perl -V>,
3725will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
44691e6f
AB
3726
3727If the bug you are reporting has security implications, which make it
e08634c5
SH
3728inappropriate to send to a publicly archived mailing list, then please send it
3729to perl5-security-report@perl.org. This points to a closed subscription
3730unarchived mailing list, which includes all the core committers, who will be
3731able to help assess the impact of issues, figure out a resolution, and help
f9001595 3732co-ordinate the release of patches to mitigate or fix the problem across all
e08634c5
SH
3733platforms on which Perl is supported. Please only use this address for
3734security issues in the Perl core, not for modules independently distributed on
3735CPAN.
44691e6f
AB
3736
3737=head1 SEE ALSO
3738
e08634c5
SH
3739The F<Changes> file for an explanation of how to view exhaustive details on
3740what changed.
44691e6f
AB
3741
3742The F<INSTALL> file for how to build Perl.
3743
3744The F<README> file for general stuff.
3745
3746The F<Artistic> and F<Copying> files for copyright information.
3747
3748=cut