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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
9be53992 350=head2 Vertical tabs are now whitespace
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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
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354breakage is expected. That said, here's what it means:
355
356C<\s> in a regex now matches a vertical tab in all circumstances.
357
358Literal vertical tabs in a regex literal are ignored when the C</x>
359modifier is used.
360
361Leading vertical tabs, alone or mixed with other whitespace, are now
362ignored when interpreting a string as a number. For example:
363
364 $dec = " \cK \t 123";
365 $hex = " \cK \t 0xF";
366
367 say 0 + $dec; # was 0 with warning, now 123
368 say int $dec; # was 0, now 123
369 say oct $hex; # was 0, now 15
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370
371=head2 C</(?{})/> and C</(??{})/> have been heavily reworked
372
373The implementation of this feature has been almost completely rewritten.
374Although its main intent is to fix bugs, some behaviors, especially
375related to the scope of lexical variables, will have changed. This is
376described more fully in the L</Selected Bug Fixes> section.
377
378=head2 Stricter parsing of substitution replacement
379
380It is no longer possible to abuse the way the parser parses C<s///e> like
381this:
382
383 %_=(_,"Just another ");
384 $_="Perl hacker,\n";
385 s//_}->{_/e;print
386
387=head2 C<given> now aliases the global C<$_>
388
389Instead of assigning to an implicit lexical C<$_>, C<given> now makes the
390global C<$_> an alias for its argument, just like C<foreach>. However, it
391still uses lexical C<$_> if there is lexical C<$_> in scope (again, just like
392C<foreach>) [perl #114020].
393
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394=head2 The smartmatch family of features are now experimental
395
396Smart match, added in v5.10.0 and significantly revised in v5.10.1, has been
397a regular point of complaint. Although there are a number of ways in which
398it is useful, it has also proven problematic and confusing for both users and
399implementors of Perl. There have been a number of proposals on how to best
400address the problem. It is clear that smartmatch is almost certainly either
401going to change or go away in the future. Relying on its current behavior
402is not recommended.
403
404Warnings will now be issued when the parser sees C<~~>, C<given>, or C<when>.
405To disable these warnings, you can add this line to the appropriate scope:
406
407 no if $] >= 5.018, "experimental::smartmatch";
408
409Consider, though, replacing the use of these features, as they may change
410behavior again before becoming stable.
411
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412=head2 Lexical C<$_> is now experimental
413
e612b5a0 414Since it was introduced in Perl v5.10, it has caused much confusion with no
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415obvious solution:
416
417=over
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418
419=item *
420
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421Various modules (e.g., List::Util) expect callback routines to use the
422global C<$_>. C<use List::Util 'first'; my $_; first { $_ == 1 } @list>
423does not work as one would expect.
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424
425=item *
426
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427A C<my $_> declaration earlier in the same file can cause confusing closure
428warnings.
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429
430=item *
431
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432The "_" subroutine prototype character allows called subroutines to access
433your lexical C<$_>, so it is not really private after all.
2426c394 434
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435=item *
436
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437Nevertheless, subroutines with a "(@)" prototype and methods cannot access
438the caller's lexical C<$_>, unless they are written in XS.
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439
440=item *
441
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442But even XS routines cannot access a lexical C<$_> declared, not in the
443calling subroutine, but in an outer scope, iff that subroutine happened not
444to mention C<$_> or use any operators that default to C<$_>.
445
446=back
447
448It is our hope that lexical C<$_> can be rehabilitated, but this may
449cause changes in its behavior. Please use it with caution until it
450becomes stable.
451
452=head2 readline() with C<$/ = \N> now reads N characters, not N bytes
453
454Previously, when reading from a stream with I/O layers such as
455C<encoding>, the readline() function, otherwise known as the C<< <> >>
456operator, would read I<N> bytes from the top-most layer. [perl #79960]
457
458Now, I<N> characters are read instead.
459
460There is no change in behaviour when reading from streams with no
461extra layers, since bytes map exactly to characters.
462
463=head2 Overridden C<glob> is now passed one argument
464
465C<glob> overrides used to be passed a magical undocumented second argument
466that identified the caller. Nothing on CPAN was using this, and it got in
467the way of a bug fix, so it was removed. If you really need to identify
468the caller, see L<Devel::Callsite> on CPAN.
469
470=head2 Here-doc parsing
471
472The body of a here-document inside a quote-like operator now always begins
473on the line after the "<<foo" marker. Previously, it was documented to
474begin on the line following the containing quote-like operator, but that
475was only sometimes the case [perl #114040].
476
477=head2 Alphanumeric operators must now be separated from the closing
478delimiter of regular expressions
479
480You may no longer write something like:
481
482 m/a/and 1
483
484Instead you must write
485
486 m/a/ and 1
487
488with whitespace separating the operator from the closing delimiter of
489the regular expression. Not having whitespace has resulted in a
490deprecation warning since Perl v5.14.0.
491
492=head2 qw(...) can no longer be used as parentheses
493
494C<qw> lists used to fool the parser into thinking they were always
495surrounded by parentheses. This permitted some surprising constructions
496such as C<foreach $x qw(a b c) {...}>, which should really be written
497C<foreach $x (qw(a b c)) {...}>. These would sometimes get the lexer into
498the wrong state, so they didn't fully work, and the similar C<foreach qw(a
499b c) {...}> that one might expect to be permitted never worked at all.
500
501This side effect of C<qw> has now been abolished. It has been deprecated
e612b5a0 502since Perl v5.13.11. It is now necessary to use real parentheses
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503everywhere that the grammar calls for them.
504
505=head2 Interaction of lexical and default warnings
506
507Turning on any lexical warnings used first to disable all default warnings
508if lexical warnings were not already enabled:
509
510 $*; # deprecation warning
511 use warnings "void";
512 $#; # void warning; no deprecation warning
513
f105b7be 514Now, the C<debugging>, C<deprecated>, C<glob>, C<inplace> and C<malloc> warnings
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515categories are left on when turning on lexical warnings (unless they are
516turned off by C<no warnings>, of course).
517
518This may cause deprecation warnings to occur in code that used to be free
519of warnings.
520
521Those are the only categories consisting only of default warnings. Default
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522warnings in other categories are still disabled by C<< use warnings "category" >>,
523as we do not yet have the infrastructure for controlling
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524individual warnings.
525
526=head2 C<state sub> and C<our sub>
527
528Due to an accident of history, C<state sub> and C<our sub> were equivalent
529to a plain C<sub>, so one could even create an anonymous sub with
530C<our sub { ... }>. These are now disallowed outside of the "lexical_subs"
531feature. Under the "lexical_subs" feature they have new meanings described
532in L<perlsub/Lexical Subroutines>.
533
534=head2 Defined values stored in environment are forced to byte strings
535
536A value stored in an environment variable has always been stringified. In this
4f5e76eb 537release, it is converted to be only a byte string. First, it is forced to be
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538only a string. Then if the string is utf8 and the equivalent of
539C<utf8::downgrade()> works, that result is used; otherwise, the equivalent of
540C<utf8::encode()> is used, and a warning is issued about wide characters
541(L</Diagnostics>).
542
543=head2 C<require> dies for unreadable files
544
545When C<require> encounters an unreadable file, it now dies. It used to
546ignore the file and continue searching the directories in C<@INC>
547[perl #113422].
548
549=head2 C<gv_fetchmeth_*> and SUPER
550
551The various C<gv_fetchmeth_*> XS functions used to treat a package whose
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552named ended with C<::SUPER> specially. A method lookup on the C<Foo::SUPER>
553package would be treated as a C<SUPER> method lookup on the C<Foo> package. This
554is no longer the case. To do a C<SUPER> lookup, pass the C<Foo> stash and the
555C<GV_SUPER> flag.
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556
557=head2 C<split>'s first argument is more consistently interpreted
558
e612b5a0 559After some changes earlier in v5.17, C<split>'s behavior has been
3853dabd 560simplified: if the PATTERN argument evaluates to a string
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561containing one space, it is treated the way that a I<literal> string
562containing one space once was.
563
564=head1 Deprecations
565
566=head2 Deprecated modules
567
568The following modules will be removed from the core distribution in a
569future release, and should be installed from CPAN instead. Distributions
570on CPAN which require these should add them to their prerequisites.
f105b7be 571The core versions of these modules will issue C<"deprecated">-category
5ed58cbd
RS
572warnings.
573
574You can silence these deprecation warnings by installing the modules
575in question from CPAN.
576
577=over
578
579=item L<Archive::Extract>
580
581=item L<B::Lint>
582
583=item L<B::Lint::Debug>
584
585=item L<CPANPLUS> and all included C<CPANPLUS::*> modules
586
587=item L<Devel::InnerPackage>
588
589=item L<encoding>
590
591=item L<Log::Message>
592
593=item L<Log::Message::Config>
594
595=item L<Log::Message::Handlers>
596
597=item L<Log::Message::Item>
598
599=item L<Log::Message::Simple>
600
601=item L<Module::Pluggable>
602
603=item L<Module::Pluggable::Object>
604
605=item L<Object::Accessor>
606
607=item L<Pod::LaTeX>
608
609=item L<Term::UI>
610
611=item L<Term::UI::History>
612
613=back
614
615=head2 Deprecated Utilities
616
617The following utilities will be removed from the core distribution in a
618future release as their associated modules have been deprecated. They
619will remain available with the applicable CPAN distribution.
620
621=over
622
623=item L<cpanp>
624
625=item C<cpanp-run-perl>
626
627=item L<cpan2dist>
628
629These items are part of the C<CPANPLUS> distribution.
630
631=item L<pod2latex>
632
633This item is part of the C<Pod::LaTeX> distribution.
634
635=back
636
637=head2 PL_sv_objcount
638
639This interpreter-global variable used to track the total number of
640Perl objects in the interpreter. It is no longer maintained and will
e612b5a0 641be removed altogether in Perl v5.20.
5ed58cbd
RS
642
643=head2 Five additional characters should be escaped in patterns with C</x>
644
645When a regular expression pattern is compiled with C</x>, Perl treats 6
646characters as white space to ignore, such as SPACE and TAB. However,
647Unicode recommends 11 characters be treated thusly. We will conform
648with this in a future Perl version. In the meantime, use of any of the
649missing characters will raise a deprecation warning, unless turned off.
650The five characters are:
f105b7be 651
c163876c
RS
652 U+0085 NEXT LINE
653 U+200E LEFT-TO-RIGHT MARK
654 U+200F RIGHT-TO-LEFT MARK
655 U+2028 LINE SEPARATOR
656 U+2029 PARAGRAPH SEPARATOR
5ed58cbd
RS
657
658=head2 User-defined charnames with surprising whitespace
659
660A user-defined character name with trailing or multiple spaces in a row is
661likely a typo. This now generates a warning when defined, on the assumption
662that uses of it will be unlikely to include the excess whitespace.
663
664=head2 Various XS-callable functions are now deprecated
665
666All the functions used to classify characters will be removed from a
667future version of Perl, and should not be used. With participating C
668compilers (e.g., gcc), compiling any file that uses any of these will
669generate a warning. These were not intended for public use; there are
670equivalent, faster, macros for most of them.
e612b5a0 671
2e7bc647 672See L<perlapi/Character classes>. The complete list is:
e612b5a0 673
5ed58cbd
RS
674C<is_uni_alnum>, C<is_uni_alnumc>, C<is_uni_alnumc_lc>,
675C<is_uni_alnum_lc>, C<is_uni_alpha>, C<is_uni_alpha_lc>,
676C<is_uni_ascii>, C<is_uni_ascii_lc>, C<is_uni_blank>,
677C<is_uni_blank_lc>, C<is_uni_cntrl>, C<is_uni_cntrl_lc>,
678C<is_uni_digit>, C<is_uni_digit_lc>, C<is_uni_graph>,
679C<is_uni_graph_lc>, C<is_uni_idfirst>, C<is_uni_idfirst_lc>,
680C<is_uni_lower>, C<is_uni_lower_lc>, C<is_uni_print>,
681C<is_uni_print_lc>, C<is_uni_punct>, C<is_uni_punct_lc>,
682C<is_uni_space>, C<is_uni_space_lc>, C<is_uni_upper>,
683C<is_uni_upper_lc>, C<is_uni_xdigit>, C<is_uni_xdigit_lc>,
684C<is_utf8_alnum>, C<is_utf8_alnumc>, C<is_utf8_alpha>,
685C<is_utf8_ascii>, C<is_utf8_blank>, C<is_utf8_char>,
686C<is_utf8_cntrl>, C<is_utf8_digit>, C<is_utf8_graph>,
687C<is_utf8_idcont>, C<is_utf8_idfirst>, C<is_utf8_lower>,
688C<is_utf8_mark>, C<is_utf8_perl_space>, C<is_utf8_perl_word>,
689C<is_utf8_posix_digit>, C<is_utf8_print>, C<is_utf8_punct>,
690C<is_utf8_space>, C<is_utf8_upper>, C<is_utf8_xdigit>,
691C<is_utf8_xidcont>, C<is_utf8_xidfirst>.
692
693In addition these three functions that have never worked properly are
694deprecated:
695C<to_uni_lower_lc>, C<to_uni_title_lc>, and C<to_uni_upper_lc>.
696
f105b7be 697=head2 Certain rare uses of backslashes within regexes are now deprecated
5ed58cbd
RS
698
699There are three pairs of characters that Perl recognizes as
700metacharacters in regular expression patterns: C<{}>, C<[]>, and C<()>.
701These can be used as well to delimit patterns, as in:
702
703 m{foo}
704 s(foo)(bar)
705
706Since they are metacharacters, they have special meaning to regular
707expression patterns, and it turns out that you can't turn off that
708special meaning by the normal means of preceding them with a backslash,
f105b7be 709if you use them, paired, within a pattern delimited by them. For
5ed58cbd
RS
710example, in
711
712 m{foo\{1,3\}}
713
714the backslashes do not change the behavior, and this matches
715S<C<"f o">> followed by one to three more occurrences of C<"o">.
716
717Usages like this, where they are interpreted as metacharacters, are
718exceedingly rare; we think there are none, for example, in all of CPAN.
719Hence, this deprecation should affect very little code. It does give
720notice, however, that any such code needs to change, which will in turn
721allow us to change the behavior in future Perl versions so that the
722backslashes do have an effect, and without fear that we are silently
723breaking any existing code.
724
d5f315e8
KW
725=head2 Splitting the tokens C<(?> and C<(*> in regular expressions
726
727A deprecation warning is now raised if the C<(> and C<?> are separated
728by white space or comments in C<(?...)> regular expression constructs.
729Similarly, if the C<(> and C<*> are separated in C<(*VERB...)>
730constructs.
731
e0a1dec5
LT
732=head2 Pre-PerlIO IO implementations
733
f3068e1b
RS
734In theory, you can currently build perl without PerlIO. Instead, you'd use a
735wrapper around stdio or sfio. In practice, this isn't very useful. It's not
736well tested, and without any support for IO layers or (thus) Unicode, it's not
737much of a perl. Building without PerlIO will most likely be removed in the
738next version of perl.
739
740PerlIO supports a C<stdio> layer if stdio use is desired. Similarly a
741sfio layer could be produced in the future, if needed.
e0a1dec5 742
5ed58cbd
RS
743=head1 Future Deprecations
744
745=over
71e6aba6
RS
746
747=item *
748
4263dd11 749Platforms without support infrastructure
5ed58cbd
RS
750
751Both Windows CE and z/OS have been historically under-maintained, and are
752currently neither successfully building nor regularly being smoke tested.
753Efforts are underway to change this situation, but it should not be taken for
754granted that the platforms are safe and supported. If they do not become
755buildable and regularly smoked, support for them may be actively removed in
756future releases. If you have an interest in these platforms and you can lend
757your time, expertise, or hardware to help support these platforms, please let
758the perl development effort know by emailing C<perl5-porters@perl.org>.
759
760Some platforms that appear otherwise entirely dead are also on the short list
e612b5a0 761for removal between now and v5.20.0:
5ed58cbd
RS
762
763=over
764
765=item DG/UX
766
767=item NeXT
768
769=back
1993add8 770
ec985017
RS
771We also think it likely that current versions of Perl will no longer
772build AmigaOS, DJGPP, NetWare (natively), OS/2 and Plan 9. If you
773are using Perl on such a platform and have an interest in ensuring
774Perl's future on them, please contact us.
775
776We believe that Perl has long been unable to build on mixed endian
ad94908e 777architectures (such as PDP-11s), and intend to remove any remaining
ec985017
RS
778support code. Similarly, code supporting the long umaintained GNU
779dld will be removed soon if no-one makes themselves known as an
780active user.
781
1993add8
RS
782=item *
783
5ed58cbd
RS
784Swapping of $< and $>
785
064fb797
LT
786Perl has supported the idiom of swapping $< and $> (and likewise $( and
787$)) to temporarily drop permissions since 5.0, like this:
788
789 ($<, $>) = ($>, $<);
790
791However, this idiom modifies the real user/group id, which can have
792undesirable side-effects, is no longer useful on any platform perl
793supports and complicates the implementation of these variables and list
794assignment in general.
795
796As an alternative, assignment only to C<< $> >> is recommended:
797
798 local $> = $<;
799
800See also: L<Setuid Demystified|http://www.cs.berkeley.edu/~daw/papers/setuid-usenix02.pdf>.
71e6aba6
RS
801
802=item *
803
5ed58cbd 804C<microperl>, long broken and of unclear present purpose, will be removed.
71e6aba6
RS
805
806=item *
807
5ed58cbd
RS
808Revamping C<< "\Q" >> semantics in double-quotish strings when combined with
809other escapes.
810
811There are several bugs and inconsistencies involving combinations
812of C<\Q> and escapes like C<\x>, C<\L>, etc., within a C<\Q...\E> pair.
813These need to be fixed, and doing so will necessarily change current
814behavior. The changes have not yet been settled.
71e6aba6 815
d5f315e8
KW
816=item *
817
818Use of C<$^>, where C<^> stands for any actual (non-printing) C0 control
819character will be disallowed in a future Perl version. Use C<${^}>
820instead (where again C<^> stands for a control character),
821or better, C<$^A> , where C<^> this time is a caret (CIRCUMFLEX ACCENT),
822and C<A> stands for any of the characters listed at the end of
823L<perlebcdic/OPERATOR DIFFERENCES>.
824
337fb649 825=back
2426c394 826
5ed58cbd
RS
827=head1 Performance Enhancements
828
829=over 4
2426c394 830
5ed58cbd 831=item *
2426c394 832
5ed58cbd
RS
833Lists of lexical variable declarations (C<my($x, $y)>) are now optimised
834down to a single op and are hence faster than before.
2426c394 835
5ed58cbd 836=item *
2426c394 837
5ed58cbd
RS
838A new C preprocessor define C<NO_TAINT_SUPPORT> was added that, if set,
839disables Perl's taint support altogether. Using the -T or -t command
840line flags will cause a fatal error. Beware that both core tests as
841well as many a CPAN distribution's tests will fail with this change. On
842the upside, it provides a small performance benefit due to reduced
843branching.
2426c394 844
5ed58cbd
RS
845B<Do not enable this unless you know exactly what you are getting yourself
846into.>
847
848=item *
849
850C<pack> with constant arguments is now constant folded in most cases
851[perl #113470].
852
853=item *
854
855Speed up in regular expression matching against Unicode properties. The
856largest gain is for C<\X>, the Unicode "extended grapheme cluster." The
857gain for it is about 35% - 40%. Bracketed character classes, e.g.,
858C<[0-9\x{100}]> containing code points above 255 are also now faster.
859
860=item *
861
862On platforms supporting it, several former macros are now implemented as static
863inline functions. This should speed things up slightly on non-GCC platforms.
864
865=item *
866
66f62cf6
RS
867The optimisation of hashes in boolean context has been extended to
868affect C<scalar(%hash)>, C<%hash ? ... : ...>, and C<sub { %hash || ... }>.
5ed58cbd
RS
869
870=item *
871
f105b7be 872Filetest operators manage the stack in a fractionally more efficient manner.
5ed58cbd
RS
873
874=item *
875
876Globs used in a numeric context are now numified directly in most cases,
f105b7be 877rather than being numified via stringification.
5ed58cbd
RS
878
879=item *
880
881The C<x> repetition operator is now folded to a single constant at compile
882time if called in scalar context with constant operands and no parentheses
883around the left operand.
884
885=back
886
887=head1 Modules and Pragmata
888
889=head2 New Modules and Pragmata
2426c394 890
337fb649 891=over 4
982110e0 892
82d98f72 893=item *
2426c394 894
5ed58cbd
RS
895L<Config::Perl::V> version 0.16 has been added as a dual-lifed module.
896It provides structured data retrieval of C<perl -V> output including
897information only known to the C<perl> binary and not available via L<Config>.
898
899=back
900
901=head2 Updated Modules and Pragmata
902
9863976f 903For a complete list of updates, run:
5ed58cbd 904
f105b7be 905 $ corelist --diff 5.16.0 5.18.0
5ed58cbd 906
e612b5a0 907You can substitute your favorite version in place of C<5.16.0>, too.
5ed58cbd 908
357b01df
AAS
909=over
910
911=item *
912
606e21ea 913L<Archive::Extract> has been upgraded to 0.68.
357b01df
AAS
914
915Work around an edge case on Linux with Busybox's unzip.
916
917=item *
918
606e21ea 919L<Archive::Tar> has been upgraded to 1.90.
357b01df
AAS
920
921ptar now supports the -T option as well as dashless options
922[rt.cpan.org #75473], [rt.cpan.org #75475].
923
924Auto-encode filenames marked as UTF-8 [rt.cpan.org #75474].
925
926Don't use C<tell> on L<IO::Zlib> handles [rt.cpan.org #64339].
927
928Don't try to C<chown> on symlinks.
929
930=item *
931
606e21ea 932L<autodie> has been upgraded to 2.13.
357b01df
AAS
933
934C<autodie> now plays nicely with the 'open' pragma.
935
936=item *
937
606e21ea 938L<B> has been upgraded to 1.42.
357b01df
AAS
939
940The C<stashoff> method of COPs has been added. This provides access to an
941internal field added in perl 5.16 under threaded builds [perl #113034].
942
943C<B::COP::stashpv> now supports UTF-8 package names and embedded NULs.
944
945All C<CVf_*> and C<GVf_*>
946and more SV-related flag values are now provided as constants in the C<B::>
947namespace and available for export. The default export list has not changed.
948
949This makes the module work with the new pad API.
950
951=item *
952
606e21ea 953L<B::Concise> has been upgraded to 0.95.
357b01df
AAS
954
955The C<-nobanner> option has been fixed, and C<format>s can now be dumped.
956When passed a sub name to dump, it will check also to see whether it
957is the name of a format. If a sub and a format share the same name,
958it will dump both.
959
960This adds support for the new C<OpMAYBE_TRUEBOOL> and C<OPpTRUEBOOL> flags.
961
962=item *
963
606e21ea 964L<B::Debug> has been upgraded to 1.18.
357b01df
AAS
965
966This adds support (experimentally) for C<B::PADLIST>, which will be
967added in Perl 5.17.4.
968
969=item *
970
606e21ea 971L<B::Deparse> has been upgraded to 1.20.
357b01df
AAS
972
973Avoid warning when run under C<perl -w>.
974
975It now deparses
976loop controls with the correct precedence, and multiple statements in a
977C<format> line are also now deparsed correctly.
978
979This release suppresses trailing semicolons in formats.
980
981This release adds stub deparsing for lexical subroutines.
982
983It no longer dies when deparsing C<sort> without arguments. It now
984correctly omits the comma for C<system $prog @args> and C<exec $prog
985@args>.
986
987=item *
988
606e21ea 989L<bignum>, L<bigint> and L<bigrat> have been upgraded to 0.33.
357b01df
AAS
990
991The overrides for C<hex> and C<oct> have been rewritten, eliminating
992several problems, and making one incompatible change:
993
994=over
995
996=item *
997
998Formerly, whichever of C<use bigint> or C<use bigrat> was compiled later
999would take precedence over the other, causing C<hex> and C<oct> not to
1000respect the other pragma when in scope.
1001
1002=item *
1003
1004Using any of these three pragmata would cause C<hex> and C<oct> anywhere
1005else in the program to evalute their arguments in list context and prevent
1006them from inferring $_ when called without arguments.
1007
1008=item *
1009
1010Using any of these three pragmata would make C<oct("1234")> return 1234
1011(for any number not beginning with 0) anywhere in the program. Now "1234"
1012is translated from octal to decimal, whether within the pragma's scope or
1013not.
1014
1015=item *
1016
1017The global overrides that facilitate lexical use of C<hex> and C<oct> now
1018respect any existing overrides that were in place before the new overrides
1019were installed, falling back to them outside of the scope of C<use bignum>.
1020
1021=item *
1022
1023C<use bignum "hex">, C<use bignum "oct"> and similar invocations for bigint
1024and bigrat now export a C<hex> or C<oct> function, instead of providing a
1025global override.
1026
1027=back
1028
1029=item *
1030
a0932e7e 1031L<Carp> has been upgraded to 1.29.
357b01df
AAS
1032
1033Carp is no longer confused when C<caller> returns undef for a package that
1034has been deleted.
1035
1036The C<longmess()> and C<shortmess()> functions are now documented.
1037
1038=item *
1039
606e21ea 1040L<CGI> has been upgraded to 3.63.
357b01df
AAS
1041
1042Unrecognized HTML escape sequences are now handled better, problematic
1043trailing newlines are no longer inserted after E<lt>formE<gt> tags
1044by C<startform()> or C<start_form()>, and bogus "Insecure Dependency"
1045warnings appearing with some versions of perl are now worked around.
1046
1047=item *
1048
606e21ea 1049L<Class::Struct> has been upgraded to 0.64.
357b01df
AAS
1050
1051The constructor now respects overridden accessor methods [perl #29230].
1052
1053=item *
1054
606e21ea 1055L<Compress::Raw::Bzip2> has been upgraded to 2.060.
357b01df
AAS
1056
1057The misuse of Perl's "magic" API has been fixed.
1058
1059=item *
1060
606e21ea 1061L<Compress::Raw::Zlib> has been upgraded to 2.060.
357b01df
AAS
1062
1063Upgrade bundled zlib to version 1.2.7.
1064
1065Fix build failures on Irix, Solaris, and Win32, and also when building as C++
1066[rt.cpan.org #69985], [rt.cpan.org #77030], [rt.cpan.org #75222].
1067
1068The misuse of Perl's "magic" API has been fixed.
1069
1070C<compress()>, C<uncompress()>, C<memGzip()> and C<memGunzip()> have
1071been speeded up by making parameter validation more efficient.
1072
1073=item *
1074
606e21ea 1075L<CPAN::Meta::Requirements> has been upgraded to 2.122.
357b01df
AAS
1076
1077Treat undef requirements to C<from_string_hash> as 0 (with a warning).
1078
1079Added C<requirements_for_module> method.
1080
1081=item *
1082
606e21ea 1083L<CPANPLUS> has been upgraded to 0.9135.
357b01df
AAS
1084
1085Allow adding F<blib/script> to PATH.
1086
1087Save the history between invocations of the shell.
1088
1089Handle multiple C<makemakerargs> and C<makeflags> arguments better.
1090
1091This resolves issues with the SQLite source engine.
1092
1093=item *
1094
606e21ea 1095L<Data::Dumper> has been upgraded to 2.145.
357b01df
AAS
1096
1097It has been optimized to only build a seen-scalar hash as necessary,
1098thereby speeding up serialization drastically.
1099
1100Additional tests were added in order to improve statement, branch, condition
1101and subroutine coverage. On the basis of the coverage analysis, some of the
1102internals of Dumper.pm were refactored. Almost all methods are now
1103documented.
1104
1105=item *
1106
606e21ea 1107L<DB_File> has been upgraded to 1.827.
357b01df
AAS
1108
1109The main Perl module no longer uses the C<"@_"> construct.
1110
1111=item *
1112
606e21ea 1113L<Devel::Peek> has been upgraded to 1.11.
357b01df
AAS
1114
1115This fixes compilation with C++ compilers and makes the module work with
1116the new pad API.
1117
1118=item *
1119
606e21ea 1120L<Digest::MD5> has been upgraded to 2.52.
357b01df
AAS
1121
1122Fix C<Digest::Perl::MD5> OO fallback [rt.cpan.org #66634].
1123
1124=item *
1125
606e21ea 1126L<Digest::SHA> has been upgraded to 5.84.
357b01df
AAS
1127
1128This fixes a double-free bug, which might have caused vulnerabilities
1129in some cases.
1130
1131=item *
1132
606e21ea 1133L<DynaLoader> has been upgraded to 1.18.
357b01df
AAS
1134
1135This is due to a minor code change in the XS for the VMS implementation.
1136
1137This fixes warnings about using C<CODE> sections without an C<OUTPUT>
1138section.
1139
1140=item *
1141
606e21ea 1142L<Encode> has been upgraded to 2.49.
357b01df
AAS
1143
1144The Mac alias x-mac-ce has been added, and various bugs have been fixed
1145in Encode::Unicode, Encode::UTF7 and Encode::GSM0338.
1146
1147=item *
1148
606e21ea 1149L<Env> has been upgraded to 1.04.
357b01df
AAS
1150
1151Its SPLICE implementation no longer misbehaves in list context.
1152
1153=item *
1154
606e21ea 1155L<ExtUtils::CBuilder> has been upgraded to 0.280210.
357b01df
AAS
1156
1157Manifest files are now correctly embedded for those versions of VC++ which
1158make use of them. [perl #111782, #111798].
1159
1160A list of symbols to export can now be passed to C<link()> when on
1161Windows, as on other OSes [perl #115100].
1162
1163=item *
1164
606e21ea 1165L<ExtUtils::ParseXS> has been upgraded to 3.18.
357b01df
AAS
1166
1167The generated C code now avoids unnecessarily incrementing
1168C<PL_amagic_generation> on Perl versions where it's done automatically
1169(or on current Perl where the variable no longer exists).
1170
1171This avoids a bogus warning for initialised XSUB non-parameters [perl
1172#112776].
1173
1174=item *
1175
606e21ea 1176L<File::Copy> has been upgraded to 2.26.
357b01df
AAS
1177
1178C<copy()> no longer zeros files when copying into the same directory,
1179and also now fails (as it has long been documented to do) when attempting
1180to copy a file over itself.
1181
1182=item *
1183
606e21ea 1184L<File::DosGlob> has been upgraded to 1.10.
357b01df
AAS
1185
1186The internal cache of file names that it keeps for each caller is now
1187freed when that caller is freed. This means
1188C<< use File::DosGlob 'glob'; eval 'scalar <*>' >> no longer leaks memory.
1189
1190=item *
1191
606e21ea 1192L<File::Fetch> has been upgraded to 0.38.
357b01df
AAS
1193
1194Added the 'file_default' option for URLs that do not have a file
1195component.
1196
1197Use C<File::HomeDir> when available, and provide C<PERL5_CPANPLUS_HOME> to
1198override the autodetection.
1199
1200Always re-fetch F<CHECKSUMS> if C<fetchdir> is set.
1201
1202=item *
1203
606e21ea 1204L<File::Find> has been upgraded to 1.23.
357b01df
AAS
1205
1206This fixes inconsistent unixy path handling on VMS.
1207
1208Individual files may now appear in list of directories to be searched
1209[perl #59750].
1210
1211=item *
1212
606e21ea 1213L<File::Glob> has been upgraded to 1.20.
357b01df
AAS
1214
1215File::Glob has had exactly the same fix as File::DosGlob. Since it is
1216what Perl's own C<glob> operator itself uses (except on VMS), this means
1217C<< eval 'scalar <*>' >> no longer leaks.
1218
1219A space-separated list of patterns return long lists of results no longer
1220results in memory corruption or crashes. This bug was introduced in
1221Perl 5.16.0. [perl #114984]
1222
1223=item *
1224
606e21ea 1225L<File::Spec::Unix> has been upgraded to 3.40.
357b01df
AAS
1226
1227C<abs2rel> could produce incorrect results when given two relative paths or
1228the root directory twice [perl #111510].
1229
1230=item *
1231
606e21ea 1232L<File::stat> has been upgraded to 1.07.
357b01df
AAS
1233
1234C<File::stat> ignores the L<filetest> pragma, and warns when used in
1235combination therewith. But it was not warning for C<-r>. This has been
1236fixed [perl #111640].
1237
1238C<-p> now works, and does not return false for pipes [perl #111638].
1239
1240Previously C<File::stat>'s overloaded C<-x> and C<-X> operators did not give
1241the correct results for directories or executable files when running as
1242root. They had been treating executable permissions for root just like for
1243any other user, performing group membership tests I<etc> for files not owned
1244by root. They now follow the correct Unix behaviour - for a directory they
1245are always true, and for a file if any of the three execute permission bits
1246are set then they report that root can execute the file. Perl's builtin
1247C<-x> and C<-X> operators have always been correct.
1248
1249=item *
1250
606e21ea 1251L<File::Temp> has been upgraded to 0.23
357b01df
AAS
1252
1253Fixes various bugs involving directory removal. Defers unlinking tempfiles if
1254the initial unlink fails, which fixes problems on NFS.
1255
1256=item *
1257
606e21ea 1258L<GDBM_File> has been upgraded to 1.15.
357b01df
AAS
1259
1260The undocumented optional fifth parameter to C<TIEHASH> has been
1261removed. This was intended to provide control of the callback used by
1262C<gdbm*> functions in case of fatal errors (such as filesystem problems),
1263but did not work (and could never have worked). No code on CPAN even
1264attempted to use it. The callback is now always the previous default,
1265C<croak>. Problems on some platforms with how the C<C> C<croak> function
1266is called have also been resolved.
1267
1268=item *
1269
606e21ea 1270L<Hash::Util> has been upgraded to 0.15.
357b01df
AAS
1271
1272C<hash_unlocked> and C<hashref_unlocked> now returns true if the hash is
1273unlocked, instead of always returning false [perl #112126].
1274
1275C<hash_unlocked>, C<hashref_unlocked>, C<lock_hash_recurse> and
1276C<unlock_hash_recurse> are now exportable [perl #112126].
1277
1278Two new functions, C<hash_locked> and C<hashref_locked>, have been added.
1279Oddly enough, these two functions were already exported, even though they
1280did not exist [perl #112126].
1281
1282=item *
1283
606e21ea 1284L<HTTP::Tiny> has been upgraded to 0.025.
357b01df
AAS
1285
1286Add SSL verification features [github #6], [github #9].
1287
1288Include the final URL in the response hashref.
1289
1290Add C<local_address> option.
1291
1292This improves SSL support.
1293
1294=item *
1295
606e21ea 1296L<IO> has been upgraded to 1.28.
357b01df
AAS
1297
1298C<sync()> can now be called on read-only file handles [perl #64772].
1299
1300L<IO::Socket> tries harder to cache or otherwise fetch socket
1301information.
1302
1303=item *
1304
606e21ea 1305L<IPC::Cmd> has been upgraded to 0.80.
357b01df
AAS
1306
1307Use C<POSIX::_exit> instead of C<exit> in C<run_forked> [rt.cpan.org #76901].
1308
1309=item *
1310
606e21ea 1311L<IPC::Open3> has been upgraded to 1.13.
357b01df
AAS
1312
1313The C<open3()> function no longer uses C<POSIX::close()> to close file
1314descriptors since that breaks the ref-counting of file descriptors done by
1315PerlIO in cases where the file descriptors are shared by PerlIO streams,
1316leading to attempts to close the file descriptors a second time when
1317any such PerlIO streams are closed later on.
1318
1319=item *
1320
606e21ea 1321L<Locale::Codes> has been upgraded to 3.25.
357b01df
AAS
1322
1323It includes some new codes.
1324
1325=item *
1326
606e21ea 1327L<Memoize> has been upgraded to 1.03.
357b01df
AAS
1328
1329Fix the C<MERGE> cache option.
1330
1331=item *
1332
606e21ea 1333L<Module::Build> has been upgraded to 0.4003.
357b01df
AAS
1334
1335Fixed bug where modules without C<$VERSION> might have a version of '0' listed
1336in 'provides' metadata, which will be rejected by PAUSE.
1337
1338Fixed bug in PodParser to allow numerals in module names.
1339
1340Fixed bug where giving arguments twice led to them becoming arrays, resulting
1341in install paths like F<ARRAY(0xdeadbeef)/lib/Foo.pm>.
1342
1343A minor bug fix allows markup to be used around the leading "Name" in
1344a POD "abstract" line, and some documentation improvements have been made.
1345
1346=item *
1347
606e21ea 1348L<Module::CoreList> has been upgraded to 2.90
357b01df
AAS
1349
1350Version information is now stored as a delta, which greatly reduces the
1351size of the F<CoreList.pm> file.
1352
1353This restores compatibility with older versions of perl and cleans up
1354the corelist data for various modules.
1355
1356=item *
1357
606e21ea 1358L<Module::Load::Conditional> has been upgraded to 0.54.
357b01df
AAS
1359
1360Fix use of C<requires> on perls installed to a path with spaces.
1361
1362Various enhancements include the new use of Module::Metadata.
1363
1364=item *
1365
606e21ea 1366L<Module::Metadata> has been upgraded to 1.000011.
357b01df
AAS
1367
1368The creation of a Module::Metadata object for a typical module file has
1369been sped up by about 40%, and some spurious warnings about C<$VERSION>s
1370have been suppressed.
1371
1372=item *
1373
606e21ea 1374L<Module::Pluggable> has been upgraded to 4.7.
357b01df
AAS
1375
1376Amongst other changes, triggers are now allowed on events, which gives
1377a powerful way to modify behaviour.
1378
1379=item *
1380
606e21ea 1381L<Net::Ping> has been upgraded to 2.41.
357b01df
AAS
1382
1383This fixes some test failures on Windows.
1384
1385=item *
1386
606e21ea 1387L<Opcode> has been upgraded to 1.25.
357b01df
AAS
1388
1389Reflect the removal of the boolkeys opcode and the addition of the
1390clonecv, introcv and padcv opcodes.
1391
1392=item *
1393
606e21ea 1394L<overload> has been upgraded to 1.22.
357b01df
AAS
1395
1396C<no overload> now warns for invalid arguments, just like C<use overload>.
1397
1398=item *
1399
606e21ea 1400L<PerlIO::encoding> has been upgraded to 0.16.
357b01df
AAS
1401
1402This is the module implementing the ":encoding(...)" I/O layer. It no
1403longer corrupts memory or crashes when the encoding back-end reallocates
1404the buffer or gives it a typeglob or shared hash key scalar.
1405
1406=item *
1407
606e21ea 1408L<PerlIO::scalar> has been upgraded to 0.16.
357b01df
AAS
1409
1410The buffer scalar supplied may now only contain code pounts 0xFF or
1411lower. [perl #109828]
1412
1413=item *
1414
606e21ea 1415L<Perl::OSType> has been upgraded to 1.003.
357b01df
AAS
1416
1417This fixes a bug detecting the VOS operating system.
1418
1419=item *
1420
606e21ea 1421L<Pod::Html> has been upgraded to 1.18.
357b01df
AAS
1422
1423The option C<--libpods> has been reinstated. It is deprecated, and its use
1424does nothing other than issue a warning that it is no longer supported.
1425
1426Since the HTML files generated by pod2html claim to have a UTF-8 charset,
1427actually write the files out using UTF-8 [perl #111446].
1428
1429=item *
1430
606e21ea 1431L<Pod::Simple> has been upgraded to 3.28.
357b01df
AAS
1432
1433Numerous improvements have been made, mostly to Pod::Simple::XHTML,
1434which also has a compatibility change: the C<codes_in_verbatim> option
1435is now disabled by default. See F<cpan/Pod-Simple/ChangeLog> for the
1436full details.
1437
1438=item *
1439
606e21ea 1440L<re> has been upgraded to 0.23
357b01df
AAS
1441
1442Single character [class]es like C</[s]/> or C</[s]/i> are now optimized
1443as if they did not have the brackets, i.e. C</s/> or C</s/i>.
1444
1445See note about C<op_comp> in the L</Internal Changes> section below.
1446
1447=item *
1448
606e21ea 1449L<Safe> has been upgraded to 2.35.
357b01df
AAS
1450
1451Fix interactions with C<Devel::Cover>.
1452
1453Don't eval code under C<no strict>.
1454
1455=item *
1456
606e21ea 1457L<Scalar::Util> has been upgraded to version 1.27.
357b01df
AAS
1458
1459Fix an overloading issue with C<sum>.
1460
1461C<first> and C<reduce> now check the callback first (so C<&first(1)> is
1462disallowed).
1463
1464Fix C<tainted> on magical values [rt.cpan.org #55763].
1465
1466Fix C<sum> on previously magical values [rt.cpan.org #61118].
1467
1468Fix reading past the end of a fixed buffer [rt.cpan.org #72700].
1469
1470=item *
1471
606e21ea 1472L<Search::Dict> has been upgraded to 1.07.
357b01df
AAS
1473
1474No longer require C<stat> on filehandles.
1475
1476Use C<fc> for casefolding.
1477
1478=item *
1479
606e21ea 1480L<Socket> has been upgraded to 2.009.
357b01df
AAS
1481
1482Constants and functions required for IP multicast source group membership
1483have been added.
1484
1485C<unpack_sockaddr_in()> and C<unpack_sockaddr_in6()> now return just the IP
1486address in scalar context, and C<inet_ntop()> now guards against incorrect
1487length scalars being passed in.
1488
1489This fixes an uninitialized memory read.
1490
1491=item *
1492
606e21ea 1493L<Storable> has been upgraded to 2.41.
357b01df
AAS
1494
1495Modifying C<$_[0]> within C<STORABLE_freeze> no longer results in crashes
1496[perl #112358].
1497
1498An object whose class implements C<STORABLE_attach> is now thawed only once
1499when there are multiple references to it in the structure being thawed
1500[perl #111918].
1501
1502Restricted hashes were not always thawed correctly [perl #73972].
1503
1504Storable would croak when freezing a blessed REF object with a
1505C<STORABLE_freeze()> method [perl #113880].
1506
1507It can now freeze and thaw vstrings correctly. This causes a slight
1508incompatible change in the storage format, so the format version has
1509increased to 2.9.
1510
1511This contains various bugfixes, including compatibility fixes for older
1512versions of Perl and vstring handling.
1513
1514=item *
1515
606e21ea 1516L<Sys::Syslog> has been upgraded to 0.32.
357b01df
AAS
1517
1518This contains several bug fixes relating to C<getservbyname()>,
1519C<setlogsock()>and log levels in C<syslog()>, together with fixes for
1520Windows, Haiku-OS and GNU/kFreeBSD. See F<cpan/Sys-Syslog/Changes>
1521for the full details.
1522
1523=item *
1524
606e21ea 1525L<Term::ANSIColor> has been upgraded to 4.02.
357b01df
AAS
1526
1527Add support for italics.
1528
1529Improve error handling.
1530
1531=item *
1532
606e21ea 1533L<Term::ReadLine> has been upgraded to 1.10. This fixes the
357b01df
AAS
1534use of the B<cpan> and B<cpanp> shells on Windows in the event that the current
1535drive happens to contain a F<\dev\tty> file.
1536
1537=item *
1538
606e21ea 1539L<Test::Harness> has been upgraded to 3.26.
357b01df
AAS
1540
1541Fix glob semantics on Win32 [rt.cpan.org #49732].
1542
1543Don't use C<Win32::GetShortPathName> when calling perl [rt.cpan.org #47890].
1544
1545Ignore -T when reading shebang [rt.cpan.org #64404].
1546
1547Handle the case where we don't know the wait status of the test more
1548gracefully.
1549
1550Make the test summary 'ok' line overridable so that it can be changed to a
1551plugin to make the output of prove idempotent.
1552
1553Don't run world-writable files.
1554
1555=item *
1556
606e21ea 1557L<Text::Tabs> and L<Text::Wrap> have been upgraded to
357b01df
AAS
15582012.0818. Support for Unicode combining characters has been added to them
1559both.
1560
1561=item *
1562
606e21ea 1563L<threads::shared> has been upgraded to 1.31.
357b01df
AAS
1564
1565This adds the option to warn about or ignore attempts to clone structures
1566that can't be cloned, as opposed to just unconditionally dying in
1567that case.
1568
1569This adds support for dual-valued values as created by
1570L<Scalar::Util::dualvar|Scalar::Util/"dualvar NUM, STRING">.
1571
1572=item *
1573
606e21ea 1574L<Tie::StdHandle> has been upgraded to 4.3.
357b01df
AAS
1575
1576C<READ> now respects the offset argument to C<read> [perl #112826].
1577
1578=item *
1579
606e21ea 1580L<Time::Local> has been upgraded to 1.2300.
357b01df
AAS
1581
1582Seconds values greater than 59 but less than 60 no longer cause
1583C<timegm()> and C<timelocal()> to croak.
1584
1585=item *
1586
606e21ea 1587L<Unicode::UCD> has been upgraded to 0.53.
357b01df
AAS
1588
1589This adds a function L<all_casefolds()|Unicode::UCD/all_casefolds()>
1590that returns all the casefolds.
1591
1592=item *
1593
606e21ea 1594L<Win32> has been upgraded to 0.47.
357b01df
AAS
1595
1596New APIs have been added for getting and setting the current code page.
1597
1598=back
1599
1600
5ed58cbd
RS
1601=head2 Removed Modules and Pragmata
1602
32b79602 1603=over
33392251
BF
1604
1605=item *
1606
5ed58cbd
RS
1607L<Version::Requirements> has been removed from the core distribution. It is
1608available under a different name: L<CPAN::Meta::Requirements>.
2426c394 1609
337fb649 1610=back
2426c394 1611
5ed58cbd 1612=head1 Documentation
19718730 1613
5ed58cbd
RS
1614=head2 Changes to Existing Documentation
1615
1616=head3 L<perlcheat>
82d98f72 1617
5a6a30f4 1618=over 4
b7c7d786 1619
5ed58cbd
RS
1620=item *
1621
1622L<perlcheat> has been reorganized, and a few new sections were added.
1623
1624=back
1625
1626=head3 L<perldata>
1627
1628=over 4
82d98f72 1629
5ed58cbd 1630=item *
d2d1e842 1631
5ed58cbd
RS
1632Now explicitly documents the behaviour of hash initializer lists that
1633contain duplicate keys.
f355e93d 1634
5a6a30f4 1635=back
f355e93d 1636
5ed58cbd 1637=head3 L<perldiag>
19718730 1638
19718730 1639=over 4
e14ac59b 1640
5ed58cbd
RS
1641=item *
1642
1643The explanation of symbolic references being prevented by "strict refs"
1644now doesn't assume that the reader knows what symbolic references are.
1645
1646=back
9f351b45 1647
5ed58cbd 1648=head3 L<perlfaq>
9f351b45 1649
5ed58cbd 1650=over 4
9f351b45 1651
5ed58cbd 1652=item *
7cf3104f 1653
5ed58cbd 1654L<perlfaq> has been synchronized with version 5.0150040 from CPAN.
12719193 1655
6253ee75 1656=back
216cf7fc 1657
5ed58cbd 1658=head3 L<perlfunc>
f5b73711 1659
5ed58cbd
RS
1660=over 4
1661
1662=item *
a75569c0 1663
5ed58cbd 1664The return value of C<pipe> is now documented.
a75569c0 1665
5ed58cbd 1666=item *
a75569c0 1667
5ed58cbd
RS
1668Clarified documentation of C<our>.
1669
1670=back
1671
1672=head3 L<perlop>
1673
1674=over 4
1675
1676=item *
1677
1678Loop control verbs (C<dump>, C<goto>, C<next>, C<last> and C<redo>) have always
1679had the same precedence as assignment operators, but this was not documented
1680until now.
1681
1682=back
1683
1684=head3 Diagnostics
1685
1686The following additions or changes have been made to diagnostic output,
1687including warnings and fatal error messages. For the complete list of
1688diagnostic messages, see L<perldiag>.
1689
5ed58cbd
RS
1690=head2 New Diagnostics
1691
5ed58cbd
RS
1692=head3 New Errors
1693
1694=over 4
1695
1696=item *
1697
1698L<Unterminated delimiter for here document|perldiag/"Unterminated delimiter for here document">
1699
1700This message now occurs when a here document label has an initial quotation
1701mark but the final quotation mark is missing.
1702
1703This replaces a bogus and misleading error message about not finding the label
1704itself [perl #114104].
1705
1706=item *
1707
1708L<panic: child pseudo-process was never scheduled|perldiag/"panic: child pseudo-process was never scheduled">
1709
1710This error is thrown when a child pseudo-process in the ithreads implementation
1711on Windows was not scheduled within the time period allowed and therefore was
1712not able to initialize properly [perl #88840].
1713
1714=item *
1715
1716L<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/">
1717
1718This error has been added for C<(?&0)>, which is invalid. It used to
1719produce an incomprehensible error message [perl #101666].
1720
1721=item *
1722
1723L<Can't use an undefined value as a subroutine reference|perldiag/"Can't use an undefined value as %s reference">
1724
1725Calling an undefined value as a subroutine now produces this error message.
1726It used to, but was accidentally disabled, first in Perl 5.004 for
e612b5a0 1727non-magical variables, and then in Perl v5.14 for magical (e.g., tied)
5ed58cbd
RS
1728variables. It has now been restored. In the mean time, undef was treated
1729as an empty string [perl #113576].
1730
1731=item *
1732
1733L<Experimental "%s" subs not enabled|perldiag/"Experimental "%s" subs not enabled">
1734
1735To use lexical subs, you must first enable them:
1736
1737 no warnings 'experimental::lexical_subs';
1738 use feature 'lexical_subs';
1739 my sub foo { ... }
1740
1741=back
1742
1743=head3 New Warnings
1744
1745=over 4
1746
1747=item *
1748
5cd341ec 1749L<'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
1750
1751=item *
1752
1753L<'%s' resolved to '\o{%s}%d'|perldiag/"'%s' resolved to '\o{%s}%d'">
1754
1755=item *
1756
1757L<'Trailing white-space in a charnames alias definition is deprecated'|perldiag/"Trailing white-space in a charnames alias definition is deprecated">
1758
1759=item *
1760
1761L<'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">
1762
1763=item *
1764
1765L<'Passing malformed UTF-8 to "%s" is deprecated'|perldiag/"Passing malformed UTF-8 to "%s" is deprecated">
1766
1767=item *
1768
1769L<Subroutine "&%s" is not available|perldiag/"Subroutine "&%s" is not available">
1770
1771(W closure) During compilation, an inner named subroutine or eval is
1772attempting to capture an outer lexical subroutine that is not currently
1773available. This can happen for one of two reasons. First, the lexical
1774subroutine may be declared in an outer anonymous subroutine that has not
1775yet been created. (Remember that named subs are created at compile time,
1776while anonymous subs are created at run-time.) For example,
1777
1778 sub { my sub a {...} sub f { \&a } }
1779
1780At the time that f is created, it can't capture the current the "a" sub,
1781since the anonymous subroutine hasn't been created yet. Conversely, the
1782following won't give a warning since the anonymous subroutine has by now
1783been created and is live:
1784
1785 sub { my sub a {...} eval 'sub f { \&a }' }->();
1786
1787The second situation is caused by an eval accessing a variable that has
1788gone out of scope, for example,
1789
1790 sub f {
1791 my sub a {...}
1792 sub { eval '\&a' }
1793 }
1794 f()->();
1795
1796Here, when the '\&a' in the eval is being compiled, f() is not currently
1797being executed, so its &a is not available for capture.
1798
1799=item *
1800
1801L<"%s" subroutine &%s masks earlier declaration in same %s|perldiag/"%s" subroutine &%s masks earlier declaration in same %s>
1802
1803(W misc) A "my" or "state" subroutine has been redeclared in the
1804current scope or statement, effectively eliminating all access to
1805the previous instance. This is almost always a typographical error.
1806Note that the earlier subroutine will still exist until the end of
1807the scope or until all closure references to it are destroyed.
1808
1809=item *
1810
1811L<The %s feature is experimental|perldiag/"The %s feature is experimental">
1812
1813(S experimental) This warning is emitted if you enable an experimental
1814feature via C<use feature>. Simply suppress the warning if you want
1815to use the feature, but know that in doing so you are taking the risk
1816of using an experimental feature which may change or be removed in a
1817future Perl version:
1818
1819 no warnings "experimental::lexical_subs";
1820 use feature "lexical_subs";
1821
1822=item *
1823
1824L<sleep(%u) too large|perldiag/"sleep(%u) too large">
1825
1826(W overflow) You called C<sleep> with a number that was larger than it can
1827reliably handle and C<sleep> probably slept for less time than requested.
1828
1829=item *
1830
1831L<Wide character in setenv|perldiag/"Wide character in %s">
1832
1833Attempts to put wide characters into environment variables via C<%ENV> now
1834provoke this warning.
1835
1836=item *
1837
1838"L<Invalid negative number (%s) in chr|perldiag/"Invalid negative number (%s) in chr">"
1839
1840C<chr()> now warns when passed a negative value [perl #83048].
1841
1842=item *
1843
1844"L<Integer overflow in srand|perldiag/"Integer overflow in srand">"
1845
1846C<srand()> now warns when passed a value that doesn't fit in a C<UV> (since the
1847value will be truncated rather than overflowing) [perl #40605].
1848
1849=item *
1850
1851"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">"
1852
1853Running perl with the C<-i> flag now warns if no input files are provided on
1854the command line [perl #113410].
1855
1856=back
1857
1858=head2 Changes to Existing Diagnostics
1859
1860=over 4
1861
1862=item *
1863
1864L<$* is no longer supported|perldiag/"$* is no longer supported">
1865
1866The warning that use of C<$*> and C<$#> is no longer supported is now
1867generated for every location that references them. Previously it would fail
1868to be generated if another variable using the same typeglob was seen first
1869(e.g. C<@*> before C<$*>), and would not be generated for the second and
1870subsequent uses. (It's hard to fix the failure to generate warnings at all
1871without also generating them every time, and warning every time is
1872consistent with the warnings that C<$[> used to generate.)
1873
1874=item *
1875
1876The warnings for C<\b{> and C<\B{> were added. They are a deprecation
1877warning which should be turned off by that category. One should not
1878have to turn off regular regexp warnings as well to get rid of these.
1879
1880=item *
1881
1882L<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>
1883
1884Constant overloading that returns C<undef> results in this error message.
1885For numeric constants, it used to say "Constant(undef)". "undef" has been
1886replaced with the number itself.
1887
1888=item *
1889
1890The error produced when a module cannot be loaded now includes a hint that
1891the module may need to be installed: "Can't locate hopping.pm in @INC (you
1892may need to install the hopping module) (@INC contains: ...)"
1893
1894=item *
1895
1896L<vector argument not supported with alpha versions|perldiag/vector argument not supported with alpha versions>
1897
1898This warning was not suppressable, even with C<no warnings>. Now it is
1899suppressible, and has been moved from the "internal" category to the
1900"printf" category.
1901
1902=item *
1903
1904C<< Can't do {n,m} with n > m in regex; marked by <-- HERE in m/%s/ >>
1905
1906This fatal error has been turned into a warning that reads:
1907
1908L<< Quantifier {n,m} with n > m can't match in regex | perldiag/Quantifier {n,m} with n > m can't match in regex >>
1909
1910(W regexp) Minima should be less than or equal to maxima. If you really want
1911your regexp to match something 0 times, just put {0}.
1912
1913=item *
1914
1915The "Runaway prototype" warning that occurs in bizarre cases has been
1916removed as being unhelpful and inconsistent.
1917
1918=item *
1919
1920The "Not a format reference" error has been removed, as the only case in
1921which it could be triggered was a bug.
1922
1923=item *
1924
1925The "Unable to create sub named %s" error has been removed for the same
1926reason.
1927
1928=item *
1929
1930The 'Can't use "my %s" in sort comparison' error has been downgraded to a
1931warning, '"my %s" used in sort comparison' (with 'state' instead of 'my'
1932for state variables). In addition, the heuristics for guessing whether
1933lexical $a or $b has been misused have been improved to generate fewer
1934false positives. Lexical $a and $b are no longer disallowed if they are
1935outside the sort block. Also, a named unary or list operator inside the
1936sort block no longer causes the $a or $b to be ignored [perl #86136].
1937
1938=back
1939
1940=head1 Utility Changes
1941
1942=head3 L<h2xs>
1943
1944=over 4
1945
1946=item *
1947
1948F<h2xs> no longer produces invalid code for empty defines. [perl #20636]
1949
1950=back
1951
1952=head1 Configuration and Compilation
1953
1954=over 4
1955
1956=item *
1957
1958Added C<useversionedarchname> option to Configure
1959
1960When set, it includes 'api_versionstring' in 'archname'. E.g.
1961x86_64-linux-5.13.6-thread-multi. It is unset by default.
1962
1963This feature was requested by Tim Bunce, who observed that
f105b7be 1964C<INSTALL_BASE> creates a library structure that does not
5ed58cbd
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1965differentiate by perl version. Instead, it places architecture
1966specific files in "$install_base/lib/perl5/$archname". This makes
f105b7be 1967it difficult to use a common C<INSTALL_BASE> library path with
5ed58cbd
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1968multiple versions of perl.
1969
f105b7be 1970By setting C<-Duseversionedarchname>, the $archname will be
c2959982 1971distinct for architecture I<and> API version, allowing mixed use of
f105b7be 1972C<INSTALL_BASE>.
5ed58cbd
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1973
1974=item *
1975
ff772877
RS
1976Add a C<PERL_NO_INLINE_FUNCTIONS> option
1977
f105b7be 1978If C<PERL_NO_INLINE_FUNCTIONS> is defined, don't include "inline.h"
ff772877
RS
1979
1980This permits test code to include the perl headers for definitions without
1981creating a link dependency on the perl library (which may not exist yet).
1982
1983=item *
1984
5ed58cbd
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1985Configure will honour the external C<MAILDOMAIN> environment variable, if set.
1986
1987=item *
1988
1989C<installman> no longer ignores the silent option
1990
1991=item *
1992
1993Both C<META.yml> and C<META.json> files are now included in the distribution.
1994
1995=item *
1996
1997F<Configure> will now correctly detect C<isblank()> when compiling with a C++
1998compiler.
1999
2000=item *
2001
2002The pager detection in F<Configure> has been improved to allow responses which
2003specify options after the program name, e.g. B</usr/bin/less -R>, if the user
2004accepts the default value. This helps B<perldoc> when handling ANSI escapes
2005[perl #72156].
2006
2007=back
2008
2009=head1 Testing
2010
2011=over 4
2012
2013=item *
2014
2015The test suite now has a section for tests that require very large amounts
2016of memory. These tests won't run by default; they can be enabled by
2017setting the C<PERL_TEST_MEMORY> environment variable to the number of
2018gibibytes of memory that may be safely used.
2019
2020=back
2021
2022=head1 Platform Support
2023
2024=head2 Discontinued Platforms
2025
2026=over 4
2027
2028=item BeOS
2029
2030BeOS was an operating system for personal computers developed by Be Inc,
2031initially for their BeBox hardware. The OS Haiku was written as an open
2032source replacement for/continuation of BeOS, and its perl port is current and
2033actively maintained.
2034
2035=item UTS Global
2036
2037Support code relating to UTS global has been removed. UTS was a mainframe
2038version of System V created by Amdahl, subsequently sold to UTS Global. The
e612b5a0 2039port has not been touched since before Perl v5.8.0, and UTS Global is now
5ed58cbd
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2040defunct.
2041
2042=item VM/ESA
2043
2044Support for VM/ESA has been removed. The port was tested on 2.3.0, which
2045IBM ended service on in March 2002. 2.4.0 ended service in June 2003, and
2046was superseded by Z/VM. The current version of Z/VM is V6.2.0, and scheduled
2047for end of service on 2015/04/30.
2048
2049=item MPE/IX
2050
2051Support for MPE/IX has been removed.
2052
2053=item EPOC
2054
2055Support code relating to EPOC has been removed. EPOC was a family of
2056operating systems developed by Psion for mobile devices. It was the
2057predecessor of Symbian. The port was last updated in April 2002.
2058
2059=item Rhapsody
2060
2061Support for Rhapsody has been removed.
2062
2063=back
2064
2065=head2 Platform-Specific Notes
2066
2067=head3 AIX
2068
2069Configure now always adds C<-qlanglvl=extc99> to the CC flags on AIX when
2070using xlC. This will make it easier to compile a number of XS-based modules
2071that assume C99 [perl #113778].
2072
2073=head3 clang++
2074
2075There is now a workaround for a compiler bug that prevented compiling
e612b5a0 2076with clang++ since Perl v5.15.7 [perl #112786].
5ed58cbd
RS
2077
2078=head3 C++
2079
2080When compiling the Perl core as C++ (which is only semi-supported), the
2081mathom functions are now compiled as C<extern "C">, to ensure proper
2082binary compatibility. (However, binary compatibility isn't generally
2083guaranteed anyway in the situations where this would matter.)
2084
2085=head3 Darwin
2086
2087Stop hardcoding an alignment on 8 byte boundaries to fix builds using
2088-Dusemorebits.
2089
2090=head3 Haiku
2091
2092Perl should now work out of the box on Haiku R1 Alpha 4.
2093
2094=head3 MidnightBSD
2095
2096C<libc_r> was removed from recent versions of MidnightBSD and older versions
2097work better with C<pthread>. Threading is now enabled using C<pthread> which
2098corrects build errors with threading enabled on 0.4-CURRENT.
2099
2100=head3 Solaris
2101
2102In Configure, avoid running sed commands with flags not supported on Solaris.
2103
2104=head3 VMS
2105
2106=over
2107
2108=item *
2109
2110Where possible, the case of filenames and command-line arguments is now
2111preserved by enabling the CRTL features C<DECC$EFS_CASE_PRESERVE> and
2112C<DECC$ARGV_PARSE_STYLE> at start-up time. The latter only takes effect
2113when extended parse is enabled in the process from which Perl is run.
2114
2115=item *
2116
2117The character set for Extended Filename Syntax (EFS) is now enabled by default
2118on VMS. Among other things, this provides better handling of dots in directory
05f5908f 2119names, multiple dots in filenames, and spaces in filenames. To obtain the old
5ed58cbd
RS
2120behavior, set the logical name C<DECC$EFS_CHARSET> to C<DISABLE>.
2121
2122=item *
2123
05f5908f 2124Fixed linking on builds configured with C<-Dusemymalloc=y>.
5ed58cbd
RS
2125
2126=item *
2127
05f5908f
CB
2128Experimental support for building Perl with the HP C++ compiler is available
2129by configuring with C<-Dusecxx>.
5ed58cbd
RS
2130
2131=item *
2132
2133All C header files from the top-level directory of the distribution are now
2134installed on VMS, providing consistency with a long-standing practice on other
2135platforms. Previously only a subset were installed, which broke non-core
2136extension builds for extensions that depended on the missing include files.
2137
2138=item *
2139
2140Quotes are now removed from the command verb (but not the parameters) for
2141commands spawned via C<system>, backticks, or a piped C<open>. Previously,
2142quotes on the verb were passed through to DCL, which would fail to recognize
2143the command. Also, if the verb is actually a path to an image or command
2144procedure on an ODS-5 volume, quoting it now allows the path to contain spaces.
2145
2146=item *
2147
2148The B<a2p> build has been fixed for the HP C++ compiler on OpenVMS.
2149
2150=back
2151
2152=head3 Win32
2153
2154=over
2155
2156=item *
2157
2158Perl can now be built using Microsoft's Visual C++ 2012 compiler by specifying
2159CCTYPE=MSVC110 (or MSVC110FREE if you are using the free Express edition for
2160Windows Desktop) in F<win32/Makefile>.
2161
2162=item *
2163
f105b7be 2164The option to build without C<USE_SOCKETS_AS_HANDLES> has been removed.
5ed58cbd
RS
2165
2166=item *
2167
2168Fixed a problem where perl could crash while cleaning up threads (including the
2169main thread) in threaded debugging builds on Win32 and possibly other platforms
2170[perl #114496].
2171
2172=item *
2173
2174A rare race condition that would lead to L<sleep|perlfunc/sleep> taking more
2175time than requested, and possibly even hanging, has been fixed [perl #33096].
2176
2177=item *
2178
2179C<link> on Win32 now attempts to set C<$!> to more appropriate values
2180based on the Win32 API error code. [perl #112272]
2181
2182Perl no longer mangles the environment block, e.g. when launching a new
2183sub-process, when the environment contains non-ASCII characters. Known
2184problems still remain, however, when the environment contains characters
2185outside of the current ANSI codepage (e.g. see the item about Unicode in
2186C<%ENV> in L<http://perl5.git.perl.org/perl.git/blob/HEAD:/Porting/todo.pod>).
2187[perl #113536]
2188
2189=item *
2190
2191Building perl with some Windows compilers used to fail due to a problem
2192with miniperl's C<glob> operator (which uses the C<perlglob> program)
2193deleting the PATH environment variable [perl #113798].
2194
2195=item *
2196
f105b7be 2197A new makefile option, C<USE_64_BIT_INT>, has been added to the Windows
5ed58cbd
RS
2198makefiles. Set this to "define" when building a 32-bit perl if you want
2199it to use 64-bit integers.
2200
2201Machine code size reductions, already made to the DLLs of XS modules in
e612b5a0 2202Perl v5.17.2, have now been extended to the perl DLL itself.
5ed58cbd 2203
e612b5a0 2204Building with VC++ 6.0 was inadvertently broken in Perl v5.17.2 but has
5ed58cbd
RS
2205now been fixed again.
2206
2207=back
2208
2209=head3 WinCE
2210
2211Building on WinCE is now possible once again, although more work is required
2212to fully restore a clean build.
2213
2214=head1 Internal Changes
2215
2216=over
2217
2218=item *
2219
4263dd11 2220Synonyms for the misleadingly named C<av_len()> have been created:
5ed58cbd
RS
2221C<av_top_index()> and C<av_tindex>. All three of these return the
2222number of the highest index in the array, not the number of elements it
2223contains.
2224
2225=item *
2226
2227SvUPGRADE() is no longer an expression. Originally this macro (and its
2228underlying function, sv_upgrade()) were documented as boolean, although
2229in reality they always croaked on error and never returned false. In 2005
2230the documentation was updated to specify a void return value, but
2231SvUPGRADE() was left always returning 1 for backwards compatibility. This
2232has now been removed, and SvUPGRADE() is now a statement with no return
2233value.
2234
2235So this is now a syntax error:
2236
2237 if (!SvUPGRADE(sv)) { croak(...); }
2238
2239If you have code like that, simply replace it with
2240
2241 SvUPGRADE(sv);
2242
237b9c6d 2243or to avoid compiler warnings with older perls, possibly
5ed58cbd
RS
2244
2245 (void)SvUPGRADE(sv);
2246
2247=item *
2248
2249Perl has a new copy-on-write mechanism that allows any SvPOK scalar to be
2250upgraded to a copy-on-write scalar. A reference count on the string buffer
d16360cf
RS
2251is stored in the string buffer itself. This feature is B<not enabled by
2252default>.
5ed58cbd 2253
d16360cf
RS
2254It can be enabled in a perl build by running F<Configure> with
2255B<-Accflags=-DPERL_NEW_COPY_ON_WRITE>, and we would encourage XS authors
2256to try their code with such an enabled perl, and provide feedback.
2257Unfortunately, there is not yet a good guide to updating XS code to cope
2258with COW. Until such a document is available, consult the perl5-porters
2259mailing list.
5ed58cbd 2260
d16360cf
RS
2261It breaks a few XS modules by allowing copy-on-write scalars to go
2262through code paths that never encountered them before.
5ed58cbd
RS
2263
2264=item *
2265
2266Copy-on-write no longer uses the SvFAKE and SvREADONLY flags. Hence,
2267SvREADONLY indicates a true read-only SV.
2268
2269Use the SvIsCOW macro (as before) to identify a copy-on-write scalar.
2270
2271=item *
2272
f105b7be 2273C<PL_glob_index> is gone.
5ed58cbd
RS
2274
2275=item *
2276
2277The private Perl_croak_no_modify has had its context parameter removed. It is
2278now has a void prototype. Users of the public API croak_no_modify remain
2279unaffected.
2280
2281=item *
2282
2283Copy-on-write (shared hash key) scalars are no longer marked read-only.
2284C<SvREADONLY> returns false on such an SV, but C<SvIsCOW> still returns
2285true.
2286
2287=item *
2288
2289A new op type, C<OP_PADRANGE> has been introduced. The perl peephole
2290optimiser will, where possible, substitute a single padrange op for a
2291pushmark followed by one or more pad ops, and possibly also skipping list
2292and nextstate ops. In addition, the op can carry out the tasks associated
f105b7be 2293with the RHS of a C<< my(...) = @_ >> assignment, so those ops may be optimised
5ed58cbd
RS
2294away too.
2295
2296=item *
2297
2298Case-insensitive matching inside a [bracketed] character class with a
2299multi-character fold no longer excludes one of the possibilities in the
2300circumstances that it used to. [perl #89774].
2301
2302=item *
2303
2304C<PL_formfeed> has been removed.
2305
2306=item *
2307
2308The regular expression engine no longer reads one byte past the end of the
2309target string. While for all internally well-formed scalars this should
2310never have been a problem, this change facilitates clever tricks with
2311string buffers in CPAN modules. [perl #73542]
2312
2313=item *
2314
2315Inside a BEGIN block, C<PL_compcv> now points to the currently-compiling
2316subroutine, rather than the BEGIN block itself.
2317
2318=item *
2319
2320C<mg_length> has been deprecated.
2321
2322=item *
2323
2324C<sv_len> now always returns a byte count and C<sv_len_utf8> a character
2325count. Previously, C<sv_len> and C<sv_len_utf8> were both buggy and would
2326sometimes returns bytes and sometimes characters. C<sv_len_utf8> no longer
be12dd22 2327assumes that its argument is in UTF-8. Neither of these creates UTF-8 caches
5ed58cbd
RS
2328for tied or overloaded values or for non-PVs any more.
2329
2330=item *
2331
2332C<sv_mortalcopy> now copies string buffers of shared hash key scalars when
2333called from XS modules [perl #79824].
2334
2335=item *
2336
2337C<RXf_SPLIT> and C<RXf_SKIPWHITE> are no longer used. They are now
2338#defined as 0.
2339
2340=item *
2341
2342The new C<RXf_MODIFIES_VARS> flag can be set by custom regular expression
2343engines to indicate that the execution of the regular expression may cause
2344variables to be modified. This lets C<s///> know to skip certain
2345optimisations. Perl's own regular expression engine sets this flag for the
2346special backtracking verbs that set $REGMARK and $REGERROR.
2347
2348=item *
2349
2350The APIs for accessing lexical pads have changed considerably.
2351
2352C<PADLIST>s are now longer C<AV>s, but their own type instead.
2353C<PADLIST>s now contain a C<PAD> and a C<PADNAMELIST> of C<PADNAME>s,
2354rather than C<AV>s for the pad and the list of pad names. C<PAD>s,
2355C<PADNAMELIST>s, and C<PADNAME>s are to be accessed as such through the
2356newly added pad API instead of the plain C<AV> and C<SV> APIs. See
2357L<perlapi> for details.
2358
2359=item *
2360
2361In the regex API, the numbered capture callbacks are passed an index
2362indicating what match variable is being accessed. There are special
2363index values for the C<$`, $&, $&> variables. Previously the same three
2364values were used to retrieve C<${^PREMATCH}, ${^MATCH}, ${^POSTMATCH}>
2365too, but these have now been assigned three separate values. See
2366L<perlreapi/Numbered capture callbacks>.
2367
2368=item *
2369
2370C<PL_sawampersand> was previously a boolean indicating that any of
2371C<$`, $&, $&> had been seen; it now contains three one-bit flags
2372indicating the presence of each of the variables individually.
2373
2374=item *
2375
2376The C<CV *> typemap entry now supports C<&{}> overloading and typeglobs,
2377just like C<&{...}> [perl #96872].
2378
2379=item *
2380
2381The C<SVf_AMAGIC> flag to indicate overloading is now on the stash, not the
2382object. It is now set automatically whenever a method or @ISA changes, so
2383its meaning has changed, too. It now means "potentially overloaded". When
2384the overload table is calculated, the flag is automatically turned off if
2385there is no overloading, so there should be no noticeable slowdown.
2386
2387The staleness of the overload tables is now checked when overload methods
2388are invoked, rather than during C<bless>.
2389
2390"A" magic is gone. The changes to the handling of the C<SVf_AMAGIC> flag
2391eliminate the need for it.
2392
2393C<PL_amagic_generation> has been removed as no longer necessary. For XS
2394modules, it is now a macro alias to C<PL_na>.
2395
2396The fallback overload setting is now stored in a stash entry separate from
2397overloadedness itself.
2398
2399=item *
2400
2401The character-processing code has been cleaned up in places. The changes
2402should be operationally invisible.
2403
2404=item *
2405
e612b5a0 2406The C<study> function was made a no-op in v5.16. It was simply disabled via
5ed58cbd
RS
2407a C<return> statement; the code was left in place. Now the code supporting
2408what C<study> used to do has been removed.
2409
2410=item *
2411
2412Under threaded perls, there is no longer a separate PV allocated for every
2413COP to store its package name (C<< cop->stashpv >>). Instead, there is an
2414offset (C<< cop->stashoff >>) into the new C<PL_stashpad> array, which
2415holds stash pointers.
2416
2417=item *
2418
2419In the pluggable regex API, the C<regexp_engine> struct has acquired a new
2420field C<op_comp>, which is currently just for perl's internal use, and
f105b7be 2421should be initialized to NULL by other regex plugin modules.
5ed58cbd
RS
2422
2423=item *
2424
7779650e 2425A new function C<alloccopstash> has been added to the API, but is considered
5ed58cbd
RS
2426experimental. See L<perlapi>.
2427
2428=item *
2429
2430Perl used to implement get magic in a way that would sometimes hide bugs in
4263dd11 2431code that could call mg_get() too many times on magical values. This hiding of
5ed58cbd
RS
2432errors no longer occurs, so long-standing bugs may become visible now. If
2433you see magic-related errors in XS code, check to make sure it, together
2434with the Perl API functions it uses, calls mg_get() only once on SvGMAGICAL()
2435values.
2436
2437=item *
2438
2439OP allocation for CVs now uses a slab allocator. This simplifies
2440memory management for OPs allocated to a CV, so cleaning up after a
2441compilation error is simpler and safer [perl #111462][perl #112312].
2442
2443=item *
2444
f105b7be 2445C<PERL_DEBUG_READONLY_OPS> has been rewritten to work with the new slab
5ed58cbd
RS
2446allocator, allowing it to catch more violations than before.
2447
2448=item *
2449
f105b7be
KE
2450The old slab allocator for ops, which was only enabled for C<PERL_IMPLICIT_SYS>
2451and C<PERL_DEBUG_READONLY_OPS>, has been retired.
5ed58cbd
RS
2452
2453=back
2454
2455=head1 Selected Bug Fixes
2456
2457=over 4
2458
2459=item *
2460
2461Here-doc terminators no longer require a terminating newline character when
2462they occur at the end of a file. This was already the case at the end of a
2463string eval [perl #65838].
2464
2465=item *
2466
f105b7be 2467C<-DPERL_GLOBAL_STRUCT> builds now free the global struct B<after>
5ed58cbd
RS
2468they've finished using it.
2469
2470=item *
2471
2472A trailing '/' on a path in @INC will no longer have an additional '/'
2473appended.
2474
2475=item *
2476
2477The C<:crlf> layer now works when unread data doesn't fit into its own
2478buffer. [perl #112244].
2479
2480=item *
2481
2482C<ungetc()> now handles UTF-8 encoded data. [perl #116322].
2483
2484=item *
2485
2486A bug in the core typemap caused any C types that map to the T_BOOL core
2487typemap entry to not be set, updated, or modified when the T_BOOL variable was
2488used in an OUTPUT: section with an exception for RETVAL. T_BOOL in an INPUT:
2489section was not affected. Using a T_BOOL return type for an XSUB (RETVAL)
2490was not affected. A side effect of fixing this bug is, if a T_BOOL is specified
2491in the OUTPUT: section (which previous did nothing to the SV), and a read only
2492SV (literal) is passed to the XSUB, croaks like "Modification of a read-only
2493value attempted" will happen. [perl #115796]
2494
2495=item *
2496
2497On many platforms, providing a directory name as the script name caused perl
2498to do nothing and report success. It should now universally report an error
2499and exit nonzero. [perl #61362]
2500
2501=item *
2502
2503C<sort {undef} ...> under fatal warnings no longer crashes. It had
e612b5a0 2504begun crashing in Perl v5.16.
5ed58cbd
RS
2505
2506=item *
2507
2508Stashes blessed into each other
2509(C<bless \%Foo::, 'Bar'; bless \%Bar::, 'Foo'>) no longer result in double
e612b5a0 2510frees. This bug started happening in Perl v5.16.
5ed58cbd
RS
2511
2512=item *
2513
2514Numerous memory leaks have been fixed, mostly involving fatal warnings and
2515syntax errors.
2516
2517=item *
2518
2519Some failed regular expression matches such as C<'f' =~ /../g> were not
2520resetting C<pos>. Also, "match-once" patterns (C<m?...?g>) failed to reset
2521it, too, when invoked a second time [perl #23180].
2522
2523=item *
2524
5ed58cbd
RS
2525Several bugs involving C<local *ISA> and C<local *Foo::> causing stale
2526MRO caches have been fixed.
2527
2528=item *
2529
2530Defining a subroutine when its typeglob has been aliased no longer results
e612b5a0 2531in stale method caches. This bug was introduced in Perl v5.10.
5ed58cbd
RS
2532
2533=item *
2534
2535Localising a typeglob containing a subroutine when the typeglob's package
2536has been deleted from its parent stash no longer produces an error. This
e612b5a0 2537bug was introduced in Perl v5.14.
5ed58cbd
RS
2538
2539=item *
2540
2541Under some circumstances, C<local *method=...> would fail to reset method
2542caches upon scope exit.
2543
2544=item *
2545
2546C</[.foo.]/> is no longer an error, but produces a warning (as before) and
2547is treated as C</[.fo]/> [perl #115818].
2548
2549=item *
2550
2551C<goto $tied_var> now calls FETCH before deciding what type of goto
2552(subroutine or label) this is.
2553
2554=item *
2555
2556Renaming packages through glob assignment
2557(C<*Foo:: = *Bar::; *Bar:: = *Baz::>) in combination with C<m?...?> and
2558C<reset> no longer makes threaded builds crash.
2559
2560=item *
2561
2562A number of bugs related to assigning a list to hash have been fixed. Many of
2563these involve lists with repeated keys like C<(1, 1, 1, 1)>.
2564
2565=over 4
2566
2567=item *
2568
2569The expression C<scalar(%h = (1, 1, 1, 1))> now returns C<4>, not C<2>.
2570
2571=item *
2572
2573The return value of C<%h = (1, 1, 1)> in list context was wrong. Previously
2574this would return C<(1, undef, 1)>, now it returns C<(1, undef)>.
2575
2576=item *
2577
2578Perl now issues the same warning on C<($s, %h) = (1, {})> as it does for
2579C<(%h) = ({})>, "Reference found where even-sized list expected".
2580
2581=item *
2582
2583A number of additional edge cases in list assignment to hashes were
2584corrected. For more details see commit 23b7025ebc.
2585
2586=back
2587
2588=item *
2589
2590Attributes applied to lexical variables no longer leak memory.
2591[perl #114764]
2592
2593=item *
2594
2595C<dump>, C<goto>, C<last>, C<next>, C<redo> or C<require> followed by a
2596bareword (or version) and then an infix operator is no longer a syntax
2597error. It used to be for those infix operators (like C<+>) that have a
2598different meaning where a term is expected. [perl #105924]
2599
2600=item *
2601
2602C<require a::b . 1> and C<require a::b + 1> no longer produce erroneous
2603ambiguity warnings. [perl #107002]
2604
2605=item *
2606
2607Class method calls are now allowed on any string, and not just strings
2608beginning with an alphanumeric character. [perl #105922]
2609
2610=item *
2611
2612An empty pattern created with C<qr//> used in C<m///> no longer triggers
2613the "empty pattern reuses last pattern" behaviour. [perl #96230]
2614
2615=item *
2616
2617Tying a hash during iteration no longer results in a memory leak.
2618
2619=item *
2620
2621Freeing a tied hash during iteration no longer results in a memory leak.
2622
2623=item *
2624
2625List assignment to a tied array or hash that dies on STORE no longer
2626results in a memory leak.
2627
2628=item *
2629
2630If the hint hash (C<%^H>) is tied, compile-time scope entry (which copies
2631the hint hash) no longer leaks memory if FETCH dies. [perl #107000]
2632
2633=item *
2634
2635Constant folding no longer inappropriately triggers the special
2636C<split " "> behaviour. [perl #94490]
2637
2638=item *
2639
2640C<defined scalar(@array)>, C<defined do { &foo }>, and similar constructs
2641now treat the argument to C<defined> as a simple scalar. [perl #97466]
2642
2643=item *
2644
2645Running a custom debugging that defines no C<*DB::DB> glob or provides a
2646subroutine stub for C<&DB::DB> no longer results in a crash, but an error
2647instead. [perl #114990]
2648
2649=item *
2650
2651C<reset ""> now matches its documentation. C<reset> only resets C<m?...?>
2652patterns when called with no argument. An empty string for an argument now
2653does nothing. (It used to be treated as no argument.) [perl #97958]
2654
2655=item *
2656
2657C<printf> with an argument returning an empty list no longer reads past the
2658end of the stack, resulting in erratic behaviour. [perl #77094]
2659
2660=item *
2661
2662C<--subname> no longer produces erroneous ambiguity warnings.
2663[perl #77240]
2664
2665=item *
2666
2667C<v10> is now allowed as a label or package name. This was inadvertently
e612b5a0 2668broken when v-strings were added in Perl v5.6. [perl #56880]
5ed58cbd
RS
2669
2670=item *
2671
2672C<length>, C<pos>, C<substr> and C<sprintf> could be confused by ties,
2673overloading, references and typeglobs if the stringification of such
be12dd22 2674changed the internal representation to or from UTF-8. [perl #114410]
5ed58cbd
RS
2675
2676=item *
2677
2678utf8::encode now calls FETCH and STORE on tied variables. utf8::decode now
2679calls STORE (it was already calling FETCH).
2680
2681=item *
2682
2683C<$tied =~ s/$non_utf8/$utf8/> no longer loops infinitely if the tied
2684variable returns a Latin-1 string, shared hash key scalar, or reference or
2ae351f8 2685typeglob that stringifies as ASCII or Latin-1. This was a regression from
e612b5a0 2686v5.12.
5ed58cbd
RS
2687
2688=item *
2689
2690C<s///> without /e is now better at detecting when it needs to forego
2691certain optimisations, fixing some buggy cases:
2692
2693=over
2694
2695=item *
2696
2697Match variables in certain constructs (C<&&>, C<||>, C<..> and others) in
2698the replacement part; e.g., C<s/(.)/$l{$a||$1}/g>. [perl #26986]
2699
2700=item *
2701
2702Aliases to match variables in the replacement.
2703
2704=item *
2705
2706C<$REGERROR> or C<$REGMARK> in the replacement. [perl #49190]
2707
2708=item *
2709
2710An empty pattern (C<s//$foo/>) that causes the last-successful pattern to
2711be used, when that pattern contains code blocks that modify the variables
2712in the replacement.
2713
2714=back
2715
2716=item *
2717
2718The taintedness of the replacement string no longer affects the taintedness
2719of the return value of C<s///e>.
2720
2721=item *
2722
2723The C<$|> autoflush variable is created on-the-fly when needed. If this
2724happened (e.g., if it was mentioned in a module or eval) when the
2725currently-selected filehandle was a typeglob with an empty IO slot, it used
2726to crash. [perl #115206]
2727
2728=item *
2729
2730Line numbers at the end of a string eval are no longer off by one.
2731[perl #114658]
2732
2733=item *
2734
2735@INC filters (subroutines returned by subroutines in @INC) that set $_ to a
2736copy-on-write scalar no longer cause the parser to modify that string
2737buffer in place.
2738
2739=item *
2740
2741C<length($object)> no longer returns the undefined value if the object has
2742string overloading that returns undef. [perl #115260]
2743
2744=item *
2745
2746The use of C<PL_stashcache>, the stash name lookup cache for method calls, has
2747been restored,
2748
2749Commit da6b625f78f5f133 in August 2011 inadvertently broke the code that looks
2750up values in C<PL_stashcache>. As it's a only cache, quite correctly everything
2751carried on working without it.
2752
2753=item *
2754
e612b5a0 2755The error "Can't localize through a reference" had disappeared in v5.16.0
5ed58cbd 2756when C<local %$ref> appeared on the last line of an lvalue subroutine.
e612b5a0 2757This error disappeared for C<\local %$ref> in perl v5.8.1. It has now
5ed58cbd
RS
2758been restored.
2759
2760=item *
2761
2762The parsing of here-docs has been improved significantly, fixing several
2763parsing bugs and crashes and one memory leak, and correcting wrong
2764subsequent line numbers under certain conditions.
2765
2766=item *
2767
2768Inside an eval, the error message for an unterminated here-doc no longer
2769has a newline in the middle of it [perl #70836].
2770
2771=item *
2772
2773A substitution inside a substitution pattern (C<s/${s|||}//>) no longer
2774confuses the parser.
2775
2776=item *
2777
2778It may be an odd place to allow comments, but C<s//"" # hello/e> has
2779always worked, I<unless> there happens to be a null character before the
2780first #. Now it works even in the presence of nulls.
2781
2782=item *
2783
2784An invalid range in C<tr///> or C<y///> no longer results in a memory leak.
2785
2786=item *
2787
2788String eval no longer treats a semicolon-delimited quote-like operator at
2789the very end (C<eval 'q;;'>) as a syntax error.
2790
2791=item *
2792
2793C<< warn {$_ => 1} + 1 >> is no longer a syntax error. The parser used to
2794get confused with certain list operators followed by an anonymous hash and
2795then an infix operator that shares its form with a unary operator.
2796
2797=item *
2798
2799C<(caller $n)[6]> (which gives the text of the eval) used to return the
2800actual parser buffer. Modifying it could result in crashes. Now it always
2801returns a copy. The string returned no longer has "\n;" tacked on to the
2802end. The returned text also includes here-doc bodies, which used to be
2803omitted.
2804
2805=item *
2806
5cd341ec
RS
2807The UTF-8 position cache is now reset when accessing magical variables, to
2808avoid the string buffer and the UTF-8 position cache getting out of sync
5ed58cbd
RS
2809[perl #114410].
2810
2811=item *
2812
be12dd22
RS
2813Various cases of get magic being called twice for magical UTF-8
2814strings have been fixed.
5ed58cbd
RS
2815
2816=item *
2817
2818This code (when not in the presence of C<$&> etc)
2819
2820 $_ = 'x' x 1_000_000;
2821 1 while /(.)/;
2822
2823used to skip the buffer copy for performance reasons, but suffered from C<$1>
2824etc changing if the original string changed. That's now been fixed.
2825
2826=item *
2827
2828Perl doesn't use PerlIO anymore to report out of memory messages, as PerlIO
2829might attempt to allocate more memory.
2830
2831=item *
2832
2833In a regular expression, if something is quantified with C<{n,m}> where
2834C<S<n E<gt> m>>, it can't possibly match. Previously this was a fatal
2835error, but now is merely a warning (and that something won't match).
2836[perl #82954].
2837
2838=item *
2839
2840It used to be possible for formats defined in subroutines that have
2841subsequently been undefined and redefined to close over variables in the
2842wrong pad (the newly-defined enclosing sub), resulting in crashes or
2843"Bizarre copy" errors.
2844
2845=item *
2846
2847Redefinition of XSUBs at run time could produce warnings with the wrong
2848line number.
2849
2850=item *
2851
2852The %vd sprintf format does not support version objects for alpha versions.
2853It used to output the format itself (%vd) when passed an alpha version, and
2854also emit an "Invalid conversion in printf" warning. It no longer does,
2855but produces the empty string in the output. It also no longer leaks
2856memory in this case.
2857
2858=item *
2859
2860C<< $obj->SUPER::method >> calls in the main package could fail if the
2861SUPER package had already been accessed by other means.
2862
2863=item *
2864
f105b7be 2865Stash aliasing (C<< *foo:: = *bar:: >>) no longer causes SUPER calls to ignore
5ed58cbd
RS
2866changes to methods or @ISA or use the wrong package.
2867
2868=item *
2869
2870Method calls on packages whose names end in ::SUPER are no longer treated
2871as SUPER method calls, resulting in failure to find the method.
2872Furthermore, defining subroutines in such packages no longer causes them to
2873be found by SUPER method calls on the containing package [perl #114924].
2874
2875=item *
2876
2877C<\w> now matches the code points U+200C (ZERO WIDTH NON-JOINER) and U+200D
2878(ZERO WIDTH JOINER). C<\W> no longer matches these. This change is because
2879Unicode corrected their definition of what C<\w> should match.
2880
2881=item *
2882
2883C<dump LABEL> no longer leaks its label.
2884
2885=item *
2886
2887Constant folding no longer changes the behaviour of functions like C<stat()>
2888and C<truncate()> that can take either filenames or handles.
2889C<stat 1 ? foo : bar> nows treats its argument as a file name (since it is an
2890arbitrary expression), rather than the handle "foo".
2891
2892=item *
2893
2894C<truncate FOO, $len> no longer falls back to treating "FOO" as a file name if
e612b5a0 2895the filehandle has been deleted. This was broken in Perl v5.16.0.
5ed58cbd
RS
2896
2897=item *
2898
2899Subroutine redefinitions after sub-to-glob and glob-to-glob assignments no
2900longer cause double frees or panic messages.
2901
2902=item *
2903
2904C<s///> now turns vstrings into plain strings when performing a substitution,
2905even if the resulting string is the same (C<s/a/a/>).
2906
2907=item *
2908
2909Prototype mismatch warnings no longer erroneously treat constant subs as having
2910no prototype when they actually have "".
2911
2912=item *
2913
2914Constant subroutines and forward declarations no longer prevent prototype
2915mismatch warnings from omitting the sub name.
2916
2917=item *
2918
2919C<undef> on a subroutine now clears call checkers.
2920
2921=item *
2922
e612b5a0 2923The C<ref> operator started leaking memory on blessed objects in Perl v5.16.0.
5ed58cbd
RS
2924This has been fixed [perl #114340].
2925
2926=item *
2927
2928C<use> no longer tries to parse its arguments as a statement, making
2929C<use constant { () };> a syntax error [perl #114222].
2930
2931=item *
2932
2933On debugging builds, "uninitialized" warnings inside formats no longer cause
2934assertion failures.
2935
2936=item *
2937
2938On debugging builds, subroutines nested inside formats no longer cause
2939assertion failures [perl #78550].
2940
2941=item *
2942
2943Formats and C<use> statements are now permitted inside formats.
2944
2945=item *
2946
2947C<print $x> and C<sub { print $x }-E<gt>()> now always produce the same output.
2948It was possible for the latter to refuse to close over $x if the variable was
2949not active; e.g., if it was defined outside a currently-running named
2950subroutine.
2951
2952=item *
2953
2954Similarly, C<print $x> and C<print eval '$x'> now produce the same output.
2955This also allows "my $x if 0" variables to be seen in the debugger [perl
2956#114018].
2957
2958=item *
2959
2960Formats called recursively no longer stomp on their own lexical variables, but
2961each recursive call has its own set of lexicals.
2962
2963=item *
2964
2965Attempting to free an active format or the handle associated with it no longer
2966results in a crash.
2967
2968=item *
2969
2970Format parsing no longer gets confused by braces, semicolons and low-precedence
2971operators. It used to be possible to use braces as format delimiters (instead
2972of C<=> and C<.>), but only sometimes. Semicolons and low-precedence operators
2973in format argument lines no longer confuse the parser into ignoring the line's
2974return value. In format argument lines, braces can now be used for anonymous
2975hashes, instead of being treated always as C<do> blocks.
2976
2977=item *
2978
2979Formats can now be nested inside code blocks in regular expressions and other
2980quoted constructs (C</(?{...})/> and C<qq/${...}/>) [perl #114040].
2981
2982=item *
2983
2984Formats are no longer created after compilation errors.
2985
2986=item *
2987
2988Under debugging builds, the B<-DA> command line option started crashing in Perl
e612b5a0 2989v5.16.0. It has been fixed [perl #114368].
5ed58cbd
RS
2990
2991=item *
2992
2993A potential deadlock scenario involving the premature termination of a pseudo-
2994forked child in a Windows build with ithreads enabled has been fixed. This
2995resolves the common problem of the F<t/op/fork.t> test hanging on Windows [perl
2996#88840].
2997
2998=item *
2999
5ed58cbd
RS
3000The code which generates errors from C<require()> could potentially read one or
3001two bytes before the start of the filename for filenames less than three bytes
3002long and ending C</\.p?\z/>. This has now been fixed. Note that it could
3003never have happened with module names given to C<use()> or C<require()> anyway.
3004
3005=item *
3006
3007The handling of pathnames of modules given to C<require()> has been made
3008thread-safe on VMS.
3009
3010=item *
3011
d85cd26b
RS
3012Non-blocking sockets have been fixed on VMS.
3013
3014=item *
3015
5ed58cbd
RS
3016Pod can now be nested in code inside a quoted construct outside of a string
3017eval. This used to work only within string evals [perl #114040].
3018
3019=item *
3020
3021C<goto ''> now looks for an empty label, producing the "goto must have
3022label" error message, instead of exiting the program [perl #111794].
3023
3024=item *
3025
3026C<goto "\0"> now dies with "Can't find label" instead of "goto must have
3027label".
3028
3029=item *
3030
3031The C function C<hv_store> used to result in crashes when used on C<%^H>
3032[perl #111000].
3033
3034=item *
3035
3036A call checker attached to a closure prototype via C<cv_set_call_checker>
3037is now copied to closures cloned from it. So C<cv_set_call_checker> now
3038works inside an attribute handler for a closure.
3039
3040=item *
3041
3042Writing to C<$^N> used to have no effect. Now it croaks with "Modification
3043of a read-only value" by default, but that can be overridden by a custom
3044regular expression engine, as with C<$1> [perl #112184].
3045
3046=item *
3047
3048C<undef> on a control character glob (C<undef *^H>) no longer emits an
3049erroneous warning about ambiguity [perl #112456].
3050
3051=item *
3052
3053For efficiency's sake, many operators and built-in functions return the
3054same scalar each time. Lvalue subroutines and subroutines in the CORE::
3055namespace were allowing this implementation detail to leak through.
3056C<print &CORE::uc("a"), &CORE::uc("b")> used to print "BB". The same thing
3057would happen with an lvalue subroutine returning the return value of C<uc>.
3058Now the value is copied in such cases.
3059
3060=item *
3061
3062C<method {}> syntax with an empty block or a block returning an empty list
3063used to crash or use some random value left on the stack as its invocant.
3064Now it produces an error.
3065
3066=item *
3067
3068C<vec> now works with extremely large offsets (E<gt>2 GB) [perl #111730].
3069
3070=item *
3071
3072Changes to overload settings now take effect immediately, as do changes to
3073inheritance that affect overloading. They used to take effect only after
3074C<bless>.
3075
3076Objects that were created before a class had any overloading used to remain
3077non-overloaded even if the class gained overloading through C<use overload>
3078or @ISA changes, and even after C<bless>. This has been fixed
3079[perl #112708].
3080
3081=item *
3082
3083Classes with overloading can now inherit fallback values.
3084
3085=item *
3086
3087Overloading was not respecting a fallback value of 0 if there were
3088overloaded objects on both sides of an assignment operator like C<+=>
3089[perl #111856].
3090
3091=item *
3092
3093C<pos> now croaks with hash and array arguments, instead of producing
3094erroneous warnings.
3095
3096=item *
3097
3098C<while(each %h)> now implies C<while(defined($_ = each %h))>, like
3099C<readline> and C<readdir>.
3100
3101=item *
3102
3103Subs in the CORE:: namespace no longer crash after C<undef *_> when called
3104with no argument list (C<&CORE::time> with no parentheses).
3105
3106=item *
3107
3108C<unpack> no longer produces the "'/' must follow a numeric type in unpack"
3109error when it is the data that are at fault [perl #60204].
3110
3111=item *
3112
3113C<join> and C<"@array"> now call FETCH only once on a tied C<$">
3114[perl #8931].
3115
3116=item *
3117
3118Some subroutine calls generated by compiling core ops affected by a
3119C<CORE::GLOBAL> override had op checking performed twice. The checking
3120is always idempotent for pure Perl code, but the double checking can
3121matter when custom call checkers are involved.
3122
3123=item *
3124
3125A race condition used to exist around fork that could cause a signal sent to
3126the parent to be handled by both parent and child. Signals are now blocked
3127briefly around fork to prevent this from happening [perl #82580].
3128
3129=item *
3130
3131The implementation of code blocks in regular expressions, such as C<(?{})>
3132and C<(??{})>, has been heavily reworked to eliminate a whole slew of bugs.
3133The main user-visible changes are:
3134
3135=over 4
3136
3137=item *
3138
3139Code blocks within patterns are now parsed in the same pass as the
3140surrounding code; in particular it is no longer necessary to have balanced
3141braces: this now works:
3142
3143 /(?{ $x='{' })/
3144
3145This means that this error message is no longer generated:
3146
3147 Sequence (?{...}) not terminated or not {}-balanced in regex
3148
3149but a new error may be seen:
3150
3151 Sequence (?{...}) not terminated with ')'
3152
3153In addition, literal code blocks within run-time patterns are only
3154compiled once, at perl compile-time:
3155
3156 for my $p (...) {
3157 # this 'FOO' block of code is compiled once,
3158 # at the same time as the surrounding 'for' loop
3159 /$p{(?{FOO;})/;
3160 }
3161
3162=item *
3163
3164Lexical variables are now sane as regards scope, recursion and closure
3165behavior. In particular, C</A(?{B})C/> behaves (from a closure viewpoint)
3166exactly like C</A/ && do { B } && /C/>, while C<qr/A(?{B})C/> is like
3167C<sub {/A/ && do { B } && /C/}>. So this code now works how you might
3168expect, creating three regexes that match 0, 1, and 2:
3169
3170 for my $i (0..2) {
3171 push @r, qr/^(??{$i})$/;
3172 }
3173 "1" =~ $r[1]; # matches
3174
3175=item *
3176
3177The C<use re 'eval'> pragma is now only required for code blocks defined
3178at runtime; in particular in the following, the text of the C<$r> pattern is
3179still interpolated into the new pattern and recompiled, but the individual
3180compiled code-blocks within C<$r> are reused rather than being recompiled,
3181and C<use re 'eval'> isn't needed any more:
3182
3183 my $r = qr/abc(?{....})def/;
3184 /xyz$r/;
3185
3186=item *
3187
3188Flow control operators no longer crash. Each code block runs in a new
3189dynamic scope, so C<next> etc. will not see
3190any enclosing loops. C<return> returns a value
3191from the code block, not from any enclosing subroutine.
3192
3193=item *
3194
3195Perl normally caches the compilation of run-time patterns, and doesn't
3196recompile if the pattern hasn't changed, but this is now disabled if
3197required for the correct behavior of closures. For example:
3198
3199 my $code = '(??{$x})';
3200 for my $x (1..3) {
3201 # recompile to see fresh value of $x each time
3202 $x =~ /$code/;
3203 }
3204
3205=item *
3206
3207The C</msix> and C<(?msix)> etc. flags are now propagated into the return
3208value from C<(??{})>; this now works:
3209
3210 "AB" =~ /a(??{'b'})/i;
3211
3212=item *
3213
3214Warnings and errors will appear to come from the surrounding code (or for
3215run-time code blocks, from an eval) rather than from an C<re_eval>:
3216
3217 use re 'eval'; $c = '(?{ warn "foo" })'; /$c/;
3218 /(?{ warn "foo" })/;
3219
3220formerly gave:
3221
3222 foo at (re_eval 1) line 1.
3223 foo at (re_eval 2) line 1.
3224
3225and now gives:
3226
3227 foo at (eval 1) line 1.
3228 foo at /some/prog line 2.
3229
3230=back
3231
3232=item *
3233
2e7bc647
KW
3234Perl now can be recompiled to use any Unicode version. In v5.16, it
3235worked on Unicodes 6.0 and 6.1, but there were various bugs if earlier
3236releases were used; the older the release the more problems.
5ed58cbd
RS
3237
3238=item *
3239
3240C<vec> no longer produces "uninitialized" warnings in lvalue context
3241[perl #9423].
3242
3243=item *
3244
3245An optimization involving fixed strings in regular expressions could cause
3246a severe performance penalty in edge cases. This has been fixed
3247[perl #76546].
3248
3249=item *
3250
3251In certain cases, including empty subpatterns within a regular expression (such
3252as C<(?:)> or C<(?:|)>) could disable some optimizations. This has been fixed.
3253
3254=item *
3255
3256The "Can't find an opnumber" message that C<prototype> produces when passed
3257a string like "CORE::nonexistent_keyword" now passes UTF-8 and embedded
3258NULs through unchanged [perl #97478].
3259
3260=item *
3261
3262C<prototype> now treats magical variables like C<$1> the same way as
3263non-magical variables when checking for the CORE:: prefix, instead of
3264treating them as subroutine names.
3265
3266=item *
3267
3268Under threaded perls, a runtime code block in a regular expression could
3269corrupt the package name stored in the op tree, resulting in bad reads
3270in C<caller>, and possibly crashes [perl #113060].
3271
3272=item *
3273
3274Referencing a closure prototype (C<\&{$_[1]}> in an attribute handler for a
3275closure) no longer results in a copy of the subroutine (or assertion
3276failures on debugging builds).
3277
3278=item *
3279
3280C<eval '__PACKAGE__'> now returns the right answer on threaded builds if
3281the current package has been assigned over (as in
3282C<*ThisPackage:: = *ThatPackage::>) [perl #78742].
3283
3284=item *
3285
3286If a package is deleted by code that it calls, it is possible for C<caller>
3287to see a stack frame belonging to that deleted package. C<caller> could
3288crash if the stash's memory address was reused for a scalar and a
3289substitution was performed on the same scalar [perl #113486].
3290
3291=item *
3292
3293C<UNIVERSAL::can> no longer treats its first argument differently
3294depending on whether it is a string or number internally.
3295
3296=item *
3297
3298C<open> with C<< <& >> for the mode checks to see whether the third argument is
3299a number, in determining whether to treat it as a file descriptor or a handle
3300name. Magical variables like C<$1> were always failing the numeric check and
3301being treated as handle names.
3302
3303=item *
3304
3305C<warn>'s handling of magical variables (C<$1>, ties) has undergone several
3306fixes. C<FETCH> is only called once now on a tied argument or a tied C<$@>
3307[perl #97480]. Tied variables returning objects that stringify as "" are
3308no longer ignored. A tied C<$@> that happened to return a reference the
3309I<previous> time it was used is no longer ignored.
3310
3311=item *
3312
3313C<warn ""> now treats C<$@> with a number in it the same way, regardless of
3314whether it happened via C<$@=3> or C<$@="3">. It used to ignore the
3315former. Now it appends "\t...caught", as it has always done with
3316C<$@="3">.
3317
3318=item *
3319
3320Numeric operators on magical variables (e.g., S<C<$1 + 1>>) used to use
3321floating point operations even where integer operations were more appropriate,
3322resulting in loss of accuracy on 64-bit platforms [perl #109542].
3323
3324=item *
3325
3326Unary negation no longer treats a string as a number if the string happened
3327to be used as a number at some point. So, if C<$x> contains the string "dogs",
3328C<-$x> returns "-dogs" even if C<$y=0+$x> has happened at some point.
3329
3330=item *
3331
e612b5a0 3332In Perl v5.14, C<-'-10'> was fixed to return "10", not "+10". But magical
5ed58cbd
RS
3333variables (C<$1>, ties) were not fixed till now [perl #57706].
3334
3335=item *
3336
3337Unary negation now treats strings consistently, regardless of the internal
3338C<UTF8> flag.
3339
3340=item *
3341
3342A regression introduced in Perl v5.16.0 involving
3343C<tr/I<SEARCHLIST>/I<REPLACEMENTLIST>/> has been fixed. Only the first
3344instance is supposed to be meaningful if a character appears more than
3345once in C<I<SEARCHLIST>>. Under some circumstances, the final instance
3346was overriding all earlier ones. [perl #113584]
3347
3348=item *
3349
3350Regular expressions like C<qr/\87/> previously silently inserted a NUL
3351character, thus matching as if it had been written C<qr/\00087/>. Now it
3352matches as if it had been written as C<qr/87/>, with a message that the
3353sequence C<"\8"> is unrecognized.
3354
3355=item *
3356
3357C<__SUB__> now works in special blocks (C<BEGIN>, C<END>, etc.).
3358
3359=item *
3360
3361Thread creation on Windows could theoretically result in a crash if done
3362inside a C<BEGIN> block. It still does not work properly, but it no longer
3363crashes [perl #111610].
3364
3365=item *
3366
3367C<\&{''}> (with the empty string) now autovivifies a stub like any other
3368sub name, and no longer produces the "Unable to create sub" error
3369[perl #94476].
3370
3371=item *
3372
3373A regression introduced in v5.14.0 has been fixed, in which some calls
3374to the C<re> module would clobber C<$_> [perl #113750].
3375
3376=item *
3377
3378C<do FILE> now always either sets or clears C<$@>, even when the file can't be
3379read. This ensures that testing C<$@> first (as recommended by the
3380documentation) always returns the correct result.
3381
3382=item *
3383
3384The array iterator used for the C<each @array> construct is now correctly
237b9c6d
SK
3385reset when C<@array> is cleared [perl #75596]. This happens, for example, when
3386the array is globally assigned to, as in C<@array = (...)>, but not when its
5ed58cbd
RS
3387B<values> are assigned to. In terms of the XS API, it means that C<av_clear()>
3388will now reset the iterator.
3389
3390This mirrors the behaviour of the hash iterator when the hash is cleared.
3391
3392=item *
3393
3394C<< $class->can >>, C<< $class->isa >>, and C<< $class->DOES >> now return
3395correct results, regardless of whether that package referred to by C<$class>
3396exists [perl #47113].
3397
3398=item *
3399
3400Arriving signals no longer clear C<$@> [perl #45173].
3401
3402=item *
3403
3404Allow C<my ()> declarations with an empty variable list [perl #113554].
3405
3406=item *
3407
3408During parsing, subs declared after errors no longer leave stubs
3409[perl #113712].
3410
3411=item *
3412
3413Closures containing no string evals no longer hang on to their containing
3414subroutines, allowing variables closed over by outer subroutines to be
3415freed when the outer sub is freed, even if the inner sub still exists
3416[perl #89544].
3417
3418=item *
3419
3420Duplication of in-memory filehandles by opening with a "<&=" or ">&=" mode
e612b5a0 3421stopped working properly in v5.16.0. It was causing the new handle to
5ed58cbd
RS
3422reference a different scalar variable. This has been fixed [perl #113764].
3423
3424=item *
3425
3426C<qr//> expressions no longer crash with custom regular expression engines
3427that do not set C<offs> at regular expression compilation time
3428[perl #112962].
3429
3430=item *
3431
3432C<delete local> no longer crashes with certain magical arrays and hashes
3433[perl #112966].
3434
3435=item *
3436
3437C<local> on elements of certain magical arrays and hashes used not to
3438arrange to have the element deleted on scope exit, even if the element did
3439not exist before C<local>.
3440
3441=item *
3442
3443C<scalar(write)> no longer returns multiple items [perl #73690].
3444
3445=item *
3446
3447String to floating point conversions no longer misparse certain strings under
3448C<use locale> [perl #109318].
3449
3450=item *
3451
3452C<@INC> filters that die no longer leak memory [perl #92252].
3453
3454=item *
3455
3456The implementations of overloaded operations are now called in the correct
3457context. This allows, among other things, being able to properly override
3458C<< <> >> [perl #47119].
3459
3460=item *
3461
3462Specifying only the C<fallback> key when calling C<use overload> now behaves
3463properly [perl #113010].
3464
3465=item *
3466
3467C<< sub foo { my $a = 0; while ($a) { ... } } >> and
3468C<< sub foo { while (0) { ... } } >> now return the same thing [perl #73618].
3469
3470=item *
3471
3472String negation now behaves the same under C<use integer;> as it does
3473without [perl #113012].
3474
3475=item *
3476
3477C<chr> now returns the Unicode replacement character (U+FFFD) for -1,
3478regardless of the internal representation. -1 used to wrap if the argument
3479was tied or a string internally.
3480
3481=item *
3482
3483Using a C<format> after its enclosing sub was freed could crash as of
e612b5a0 3484perl v5.12.0, if the format referenced lexical variables from the outer sub.
5ed58cbd
RS
3485
3486=item *
3487
3488Using a C<format> after its enclosing sub was undefined could crash as of
e612b5a0 3489perl v5.10.0, if the format referenced lexical variables from the outer sub.
5ed58cbd
RS
3490
3491=item *
3492
3493Using a C<format> defined inside a closure, which format references
3494lexical variables from outside, never really worked unless the C<write>
e612b5a0 3495call was directly inside the closure. In v5.10.0 it even started crashing.
5ed58cbd
RS
3496Now the copy of that closure nearest the top of the call stack is used to
3497find those variables.
3498
3499=item *
3500
3501Formats that close over variables in special blocks no longer crash if a
3502stub exists with the same name as the special block before the special
3503block is compiled.
3504
3505=item *
3506
3507The parser no longer gets confused, treating C<eval foo ()> as a syntax
3508error if preceded by C<print;> [perl #16249].
3509
3510=item *
3511
3512The return value of C<syscall> is no longer truncated on 64-bit platforms
3513[perl #113980].
3514
3515=item *
3516
3517Constant folding no longer causes C<print 1 ? FOO : BAR> to print to the
3518FOO handle [perl #78064].
3519
3520=item *
3521
3522C<do subname> now calls the named subroutine and uses the file name it
3523returns, instead of opening a file named "subname".
3524
3525=item *
3526
3527Subroutines looked up by rv2cv check hooks (registered by XS modules) are
3528now taken into consideration when determining whether C<foo bar> should be
3529the sub call C<foo(bar)> or the method call C<< "bar"->foo >>.
3530
3531=item *
3532
3533C<CORE::foo::bar> is no longer treated specially, allowing global overrides
3534to be called directly via C<CORE::GLOBAL::uc(...)> [perl #113016].
3535
3536=item *
3537
3538Calling an undefined sub whose typeglob has been undefined now produces the
3539customary "Undefined subroutine called" error, instead of "Not a CODE
3540reference".
3541
3542=item *
3543
3544Two bugs involving @ISA have been fixed. C<*ISA = *glob_without_array> and
3545C<undef *ISA; @{*ISA}> would prevent future modifications to @ISA from
3546updating the internal caches used to look up methods. The
e612b5a0 3547*glob_without_array case was a regression from Perl v5.12.
5ed58cbd
RS
3548
3549=item *
3550
3551Regular expression optimisations sometimes caused C<$> with C</m> to
3552produce failed or incorrect matches [perl #114068].
3553
3554=item *
3555
3556C<__SUB__> now works in a C<sort> block when the enclosing subroutine is
3557predeclared with C<sub foo;> syntax [perl #113710].
3558
3559=item *
3560
3561Unicode properties only apply to Unicode code points, which leads to
3562some subtleties when regular expressions are matched against
3563above-Unicode code points. There is a warning generated to draw your
3564attention to this. However, this warning was being generated
3565inappropriately in some cases, such as when a program was being parsed.
3566Non-Unicode matches such as C<\w> and C<[:word;]> should not generate the
3567warning, as their definitions don't limit them to apply to only Unicode
3568code points. Now the message is only generated when matching against
3569C<\p{}> and C<\P{}>. There remains a bug, [perl #114148], for the very
3570few properties in Unicode that match just a single code point. The
3571warning is not generated if they are matched against an above-Unicode
3572code point.
3573
3574=item *
3575
3576Uninitialized warnings mentioning hash elements would only mention the
3577element name if it was not in the first bucket of the hash, due to an
3578off-by-one error.
3579
3580=item *
3581
3582A regular expression optimizer bug could cause multiline "^" to behave
3583incorrectly in the presence of line breaks, such that
3584C<"/\n\n" =~ m#\A(?:^/$)#im> would not match [perl #115242].
3585
3586=item *
3587
3588Failed C<fork> in list context no longer corrupts the stack.
3589C<@a = (1, 2, fork, 3)> used to gobble up the 2 and assign C<(1, undef, 3)>
3590if the C<fork> call failed.
3591
3592=item *
3593
3594Numerous memory leaks have been fixed, mostly involving tied variables that
3595die, regular expression character classes and code blocks, and syntax
3596errors.
3597
3598=item *
3599
3600Assigning a regular expression (C<${qr//}>) to a variable that happens to
3601hold a floating point number no longer causes assertion failures on
3602debugging builds.
3603
3604=item *
3605
3606Assigning a regular expression to a scalar containing a number no longer
f105b7be 3607causes subsequent numification to produce random numbers.
5ed58cbd
RS
3608
3609=item *
3610
3611Assigning a regular expression to a magic variable no longer wipes away the
e612b5a0 3612magic. This was a regression from v5.10.
5ed58cbd
RS
3613
3614=item *
3615
3616Assigning a regular expression to a blessed scalar no longer results in
e612b5a0 3617crashes. This was also a regression from v5.10.
5ed58cbd
RS
3618
3619=item *
3620
3621Regular expression can now be assigned to tied hash and array elements with
3622flattening into strings.
3623
3624=item *
3625
f105b7be 3626Numifying a regular expression no longer results in an uninitialized
5ed58cbd
RS
3627warning.
3628
3629=item *
3630
3631Negative array indices no longer cause EXISTS methods of tied variables to
e612b5a0 3632be ignored. This was a regression from v5.12.
5ed58cbd
RS
3633
3634=item *
3635
3636Negative array indices no longer result in crashes on arrays tied to
3637non-objects.
3638
3639=item *
3640
be12dd22
RS
3641C<$byte_overload .= $utf8> no longer results in doubly-encoded UTF-8 if the
3642left-hand scalar happened to have produced a UTF-8 string the last time
5ed58cbd
RS
3643overloading was invoked.
3644
3645=item *
3646
3647C<goto &sub> now uses the current value of @_, instead of using the array
3648the subroutine was originally called with. This means
3649C<local @_ = (...); goto &sub> now works [perl #43077].
3650
3651=item *
3652
3653If a debugger is invoked recursively, it no longer stomps on its own
3654lexical variables. Formerly under recursion all calls would share the same
3655set of lexical variables [perl #115742].
3656
3657=item *
3658
3659C<*_{ARRAY}> returned from a subroutine no longer spontaneously
3660becomes empty.
3661
3662=back
3663
3664=head1 Known Problems
3665
3666=over 4
3667
3668=item *
3669
7f50b25b 3670There are no known regressions. Please report any bugs you find!
5ed58cbd
RS
3671
3672=back
3673
32b79602
RS
3674=head1 Obituary
3675
3676Hojung Yoon (AMORETTE), 24, of Seoul, South Korea, went to his long rest
3677on May 8, 2013 with llama figurine and autographed TIMTOADY card. He
3678was a brilliant young Perl 5 & 6 hacker and a devoted member of
55c6e7a8 3679Seoul.pm. He programmed Perl, talked Perl, ate Perl, and loved Perl. We
32b79602
RS
3680believe that he is still programming in Perl with his broken IBM laptop
3681somewhere. He will be missed.
3682
5ed58cbd 3683=head1 Acknowledgements
a75569c0 3684
dd38235c
RS
3685Perl v5.18.0 represents approximately 12 months of development since
3686Perl v5.16.0 and contains approximately 400,000 lines of changes across
36872,100 files from 113 authors.
3688
3689Perl continues to flourish into its third decade thanks to a vibrant
3690community of users and developers. The following people are known to
3691have contributed the improvements that became Perl v5.18.0:
3692
3693Aaron Crane, Aaron Trevena, Abhijit Menon-Sen, Adrian M. Enache, Alan
3694Haggai Alavi, Alexandr Ciornii, Andrew Tam, Andy Dougherty, Anton Nikishaev,
3695Aristotle Pagaltzis, Augustina Blair, Bob Ernst, Brad Gilbert, Breno G. de
3696Oliveira, Brian Carlson, Brian Fraser, Charlie Gonzalez, Chip Salzenberg, Chris
3697'BinGOs' Williams, Christian Hansen, Colin Kuskie, Craig A. Berry, Dagfinn
3698Ilmari Mannsåker, Daniel Dragan, Daniel Perrett, Darin McBride, Dave Rolsky,
3699David Golden, David Leadbeater, David Mitchell, David Nicol, Dominic
3700Hargreaves, E. Choroba, Eric Brine, Evan Miller, Father Chrysostomos, Florian
3701Ragwitz, François Perrad, George Greer, Goro Fuji, H.Merijn Brand, Herbert
3702Breunung, Hugo van der Sanden, Igor Zaytsev, James E Keenan, Jan Dubois,
3703Jasmine Ahuja, Jerry D. Hedden, Jess Robinson, Jesse Luehrs, Joaquin Ferrero,
3704Joel Berger, John Goodyear, John Peacock, Karen Etheridge, Karl Williamson,
3705Karthik Rajagopalan, Kent Fredric, Leon Timmermans, Lucas Holt, Lukas Mai,
3706Marcus Holland-Moritz, Markus Jansen, Martin Hasch, Matthew Horsfall, Max
3707Maischein, Michael G Schwern, Michael Schroeder, Moritz Lenz, Nicholas Clark,
3708Niko Tyni, Oleg Nesterov, Patrik Hägglund, Paul Green, Paul Johnson, Paul
3709Marquess, Peter Martini, Rafael Garcia-Suarez, Reini Urban, Renee Baecker,
3710Rhesa Rozendaal, Ricardo Signes, Robin Barker, Ronald J. Kimball, Ruslan
3711Zakirov, Salvador Fandiño, Sawyer X, Scott Lanning, Sergey Alekseev, Shawn M
3712Moore, Shirakata Kentaro, Shlomi Fish, Sisyphus, Smylers, Steffen Müller,
3713Steve Hay, Steve Peters, Steven Schubiger, Sullivan Beck, Sven Strickroth,
3714Sébastien Aperghis-Tramoni, Thomas Sibley, Tobias Leich, Tom Wyant, Tony Cook,
3715Vadim Konovalov, Vincent Pit, Volker Schatz, Walt Mankowski, Yves Orton,
3716Zefram.
3717
3718The list above is almost certainly incomplete as it is automatically generated
3719from version control history. In particular, it does not include the names of
3720the (very much appreciated) contributors who reported issues to the Perl bug
3721tracker.
3722
3723Many of the changes included in this version originated in the CPAN modules
3724included in Perl's core. We're grateful to the entire CPAN community for
3725helping Perl to flourish.
3726
3727For a more complete list of all of Perl's historical contributors, please see
3728the F<AUTHORS> file in the Perl source distribution.
f5b73711 3729
44691e6f
AB
3730=head1 Reporting Bugs
3731
e08634c5
SH
3732If you find what you think is a bug, you might check the articles recently
3733posted to the comp.lang.perl.misc newsgroup and the perl bug database at
3734http://rt.perl.org/perlbug/ . There may also be information at
3735http://www.perl.org/ , the Perl Home Page.
44691e6f 3736
e08634c5
SH
3737If you believe you have an unreported bug, please run the L<perlbug> program
3738included with your release. Be sure to trim your bug down to a tiny but
3739sufficient test case. Your bug report, along with the output of C<perl -V>,
3740will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
44691e6f
AB
3741
3742If the bug you are reporting has security implications, which make it
e08634c5
SH
3743inappropriate to send to a publicly archived mailing list, then please send it
3744to perl5-security-report@perl.org. This points to a closed subscription
3745unarchived mailing list, which includes all the core committers, who will be
3746able to help assess the impact of issues, figure out a resolution, and help
f9001595 3747co-ordinate the release of patches to mitigate or fix the problem across all
e08634c5
SH
3748platforms on which Perl is supported. Please only use this address for
3749security issues in the Perl core, not for modules independently distributed on
3750CPAN.
44691e6f
AB
3751
3752=head1 SEE ALSO
3753
e08634c5
SH
3754The F<Changes> file for an explanation of how to view exhaustive details on
3755what changed.
44691e6f
AB
3756
3757The F<INSTALL> file for how to build Perl.
3758
3759The F<README> file for general stuff.
3760
3761The F<Artistic> and F<Copying> files for copyright information.
3762
3763=cut