5 perldelta - what is new for perl v5.14.0
9 This document describes differences between the 5.12.0 release and
12 If you are upgrading from an earlier release such as 5.10.0, first read
13 L<perl5120delta>, which describes differences between 5.10.0 and
16 Some of the bug fixes in this release have been backported to subsequent
17 releases of 5.12.x. Those are indicated with the 5.12.x version in
22 XXX Any important notices here
24 =head1 Core Enhancements
28 =head3 Unicode Version 6.0 is now supported (mostly)
30 Perl comes with the Unicode 6.0 data base updated with
31 L<Corrigendum #8|http://www.unicode.org/versions/corrigendum8.html>,
32 with one exception noted below.
33 See L<http://unicode.org/versions/Unicode6.0.0> for details on the new
34 release. Perl does not support any Unicode provisional properties,
35 including the new ones for this release.
37 Unicode 6.0 has chosen to use the name C<BELL> for the character at U+1F514,
38 which is a symbol that looks like a bell, and is used in Japanese cell
39 phones. This conflicts with the long-standing Perl usage of having
40 C<BELL> mean the ASCII C<BEL> character, U+0007. In Perl 5.14,
41 C<\N{BELL}> will continue to mean U+0007, but its use will generate a
42 deprecated warning message, unless such warnings are turned off. The
43 new name for U+0007 in Perl is C<ALERT>, which corresponds nicely
44 with the existing shorthand sequence for it, C<"\a">. C<\N{BEL}>
45 means U+0007, with no warning given. The character at U+1F514 will not
46 have a name in 5.14, but can be referred to by C<\N{U+1F514}>. The plan
47 is that in Perl 5.16, C<\N{BELL}> will refer to U+1F514, and so all code
48 that uses C<\N{BELL}> should convert by then to using C<\N{ALERT}>,
49 C<\N{BEL}>, or C<"\a"> instead.
51 =head3 Full functionality for C<use feature 'unicode_strings'>
53 This release provides full functionality for C<use feature
54 'unicode_strings'>. Under its scope, all string operations executed and
55 regular expressions compiled (even if executed outside its scope) have
56 Unicode semantics. See L<feature>.
58 This feature avoids most forms of the "Unicode Bug" (See
59 L<perlunicode/The "Unicode Bug"> for details.) If there is a
60 possibility that your code will process Unicode strings, you are
61 B<strongly> encouraged to use this subpragma to avoid nasty surprises.
63 =head3 C<\N{I<name>}> and C<charnames> enhancements
69 C<\N{}> and C<charnames::vianame> now know about the abbreviated
70 character names listed by Unicode, such as NBSP, SHY, LRO, ZWJ, etc., all
71 the customary abbreviations for the C0 and C1 control characters (such as
72 ACK, BEL, CAN, etc.), and a few new variants of some C1 full names that
77 Unicode has a number of named character sequences, in which particular sequences
78 of code points are given names. C<\N{...}> now recognizes these.
82 C<\N{}>, C<charnames::vianame>, C<charnames::viacode> now know about every
83 character in Unicode. Previously, they didn't know about the Hangul syllables
84 nor a number of CJK (Chinese/Japanese/Korean) characters.
88 In the past, it was ineffective to override one of Perl's abbreviations
89 with your own custom alias. Now it works.
93 You can also create a custom alias of the ordinal of a
94 character, known by C<\N{...}>, C<charnames::vianame()>, and
95 C<charnames::viacode()>. Previously, an alias had to be to an official
96 Unicode character name. This made it impossible to create an alias for
97 a code point that had no name, such as those reserved for private
102 A new function, C<charnames::string_vianame()>, has been added.
103 This function is a run-time version of C<\N{...}>, returning the string
104 of characters whose Unicode name is its parameter. It can handle
105 Unicode named character sequences, whereas the pre-existing
106 C<charnames::vianame()> cannot, as the latter returns a single code
111 See L<charnames> for details on all these changes.
113 =head3 New warnings categories for problematic (non-)Unicode code points.
115 Three new warnings subcategories of "utf8" have been added. These
116 allow you to turn off some "utf8" warnings, while allowing
117 others warnings to remain on. The three categories are:
118 C<surrogate> when UTF-16 surrogates are encountered;
119 C<nonchar> when Unicode non-character code points are encountered;
120 and C<non_unicode> when code points that are above the legal Unicode
121 maximum of 0x10FFFF are encountered.
123 =head3 Any unsigned value can be encoded as a character
125 With this release, Perl is adopting a model that any unsigned value can
126 be treated as a code point and encoded internally (as utf8) without
127 warnings - not just the code points that are legal in Unicode.
128 However, unless utf8 or the corresponding sub-category (see previous
129 item) warnings have been
130 explicitly lexically turned off, outputting or performing a
131 Unicode-defined operation (such as upper-casing) on such a code point
132 will generate a warning. Attempting to input these using strict rules
133 (such as with the C<:encoding('UTF-8')> layer) will continue to fail.
134 Prior to this release the handling was very inconsistent, and incorrect
135 in places. Also, the Unicode non-characters, some of which previously were
136 erroneously considered illegal in places by Perl, contrary to the Unicode
137 standard, are now always legal internally. But inputting or outputting
138 them will work the same as for the non-legal Unicode code points, as the
139 Unicode standard says they are illegal for "open interchange".
141 =head3 Unicode database files not installed
143 The Unicode database files are no longer installed with Perl. This
144 doesn't affect any functionality in Perl and saves significant disk
145 space. If you previously were explicitly opening and reading those
146 files, you can download them from
147 L<http://www.unicode.org/Public/zipped/6.0.0/>.
149 =head2 Regular Expressions
151 =head3 C<(?^...)> construct to signify default modifiers
153 An ASCII caret (also called a "circumflex accent") C<"^">
154 immediately following a C<"(?"> in a regular expression
155 now means that the subexpression does not inherit the
156 surrounding modifiers such as C</i>, but reverts to the
157 Perl defaults. Any modifiers following the caret override the defaults.
159 The stringification of regular expressions now uses this
160 notation. E.g., before, C<qr/hlagh/i> would be stringified as
161 C<(?i-xsm:hlagh)>, but now it's stringified as C<(?^i:hlagh)>.
163 The main purpose of this is to allow tests that rely on the
164 stringification not to have to change when new modifiers are added.
165 See L<perlre/Extended Patterns>.
167 =head3 C</d>, C</l>, C</u>, C</a>, and C</aa> modifiers
169 Four new regular expression modifiers have been added. These are mutually
170 exclusive; one only can be turned on at a time.
172 The C</l> modifier says to compile the regular expression as if it were
173 in the scope of C<use locale>, even if it is not.
175 The C</u> modifier says to compile the regular expression as if it were
176 in the scope of a C<use feature "unicode_strings"> pragma.
178 The C</d> (default) modifier is used to override any C<use locale> and
179 C<use feature "unicode_strings"> pragmas that are in effect at the time
180 of compiling the regular expression.
182 The C</a> regular expression modifier restricts C<\s>, C<\d> and C<\w> and
183 the Posix (C<[[:posix:]]>) character classes to the ASCII range. Their
184 complements and C<\b> and C<\B> are correspondingly
185 affected. Otherwise, C</a> behaves like the C</u> modifier, in that
186 case-insensitive matching uses Unicode semantics.
188 The C</aa> modifier is like C</a>, except that, in case-insensitive matching, no ASCII character will match a
189 non-ASCII character. For example,
191 'k' =~ /\N{KELVIN SIGN}/ai
193 will match; it won't under C</aa>.
195 See L<perlre/Modifiers> for more detail.
197 =head3 Non-destructive substitution
199 The substitution (C<s///>) and transliteration
200 (C<y///>) operators now support an C</r> option that
201 copies the input variable, carries out the substitution on
202 the copy and returns the result. The original remains unmodified.
205 my $new = $old =~ s/cat/dog/r;
206 # $old is 'cat' and $new is 'dog'
208 This is particularly useful with C<map>. See L<perlop> for more examples.
210 =head3 Reentrant regular expression engine
212 It is now safe to use regular expressions within C<(?{...})> and
213 C<(??{...})> code blocks inside regular expressions.
215 These block are still experimental, however, and still have problems with
216 lexical (C<my>) variables and abnormal exiting.
218 =head3 C<use re '/flags';>
220 The C<re> pragma now has the ability to turn on regular expression flags
221 till the end of the lexical scope:
224 "foo" =~ / (.+) /; # /x implied
226 See L<re/"'/flags' mode"> for details.
228 =head3 \o{...} for octals
230 There is a new octal escape sequence, C<"\o">, in double-quote-like
231 contexts. This construct allows large octal ordinals beyond the
232 current max of 0777 to be represented. It also allows you to specify a
233 character in octal which can safely be concatenated with other regex
234 snippets and which won't be confused with being a backreference to
235 a regex capture group. See L<perlre/Capture groups>.
237 =head3 Add C<\p{Titlecase}> as a synonym for C<\p{Title}>
239 This synonym is added for symmetry with the Unicode property names
240 C<\p{Uppercase}> and C<\p{Lowercase}>.
242 =head3 Regular expression debugging output improvement
244 Regular expression debugging output (turned on by C<use re 'debug';>) now
245 uses hexadecimal when escaping non-ASCII characters, instead of octal.
247 =head3 Return value of C<delete $+{...}>
249 Custom regular expression engines can now determine the return value of
250 C<delete> on an entry of C<%+> or C<%->.
252 =head2 Syntactical Enhancements
254 =head3 Array and hash container functions accept references
256 All built-in functions that operate directly on array or hash
257 containers now also accept hard references to arrays or hashes:
259 |----------------------------+---------------------------|
260 | Traditional syntax | Terse syntax |
261 |----------------------------+---------------------------|
262 | push @$arrayref, @stuff | push $arrayref, @stuff |
263 | unshift @$arrayref, @stuff | unshift $arrayref, @stuff |
264 | pop @$arrayref | pop $arrayref |
265 | shift @$arrayref | shift $arrayref |
266 | splice @$arrayref, 0, 2 | splice $arrayref, 0, 2 |
267 | keys %$hashref | keys $hashref |
268 | keys @$arrayref | keys $arrayref |
269 | values %$hashref | values $hashref |
270 | values @$arrayref | values $arrayref |
271 | ($k,$v) = each %$hashref | ($k,$v) = each $hashref |
272 | ($k,$v) = each @$arrayref | ($k,$v) = each $arrayref |
273 |----------------------------+---------------------------|
275 This allows these built-in functions to act on long dereferencing chains
276 or on the return value of subroutines without needing to wrap them in
279 push @{$obj->tags}, $new_tag; # old way
280 push $obj->tags, $new_tag; # new way
282 for ( keys %{$hoh->{genres}{artists}} ) {...} # old way
283 for ( keys $hoh->{genres}{artists} ) {...} # new way
285 For C<push>, C<unshift> and C<splice>, the reference will auto-vivify
286 if it is not defined, just as if it were wrapped with C<@{}>.
288 For C<keys>, C<values>, C<each>, when overloaded dereferencing is
289 present, the overloaded dereference is used instead of dereferencing the
290 underlying reftype. Warnings are issued about assumptions made in
293 =head3 Single term prototype
295 The C<+> prototype is a special alternative to C<$> that will act like
296 C<\[@%]> when given a literal array or hash variable, but will otherwise
297 force scalar context on the argument. See L<perlsub/Prototypes>.
299 =head3 C<package> block syntax
301 A package declaration can now contain a code block, in which case the
302 declaration is in scope only inside that block. So C<package Foo { ... }>
303 is precisely equivalent to C<{ package Foo; ... }>. It also works with
304 a version number in the declaration, as in C<package Foo 1.2 { ... }>.
307 =head3 Statement labels can appear in more places
309 Statement labels can now occur before any type of statement or declaration,
312 =head3 Stacked labels
314 Multiple statement labels can now appear before a single statement.
316 =head3 Uppercase X/B allowed in hexadecimal/binary literals
318 Literals may now use either upper case C<0X...> or C<0B...> prefixes,
319 in addition to the already supported C<0x...> and C<0b...>
320 syntax [perl #76296].
322 C, Ruby, Python and PHP already supported this syntax, and it makes
323 Perl more internally consistent. A round-trip with C<eval sprintf
324 "%#X", 0x10> now returns C<16>, the way C<eval sprintf "%#x", 0x10> does.
326 =head3 Overridable tie functions
328 C<tie>, C<tied> and C<untie> can now be overridden [perl #75902].
330 =head2 Exception Handling
332 Several changes have been made to the way C<die>, C<warn>, and C<$@>
333 behave, in order to make them more reliable and consistent.
335 When an exception is thrown inside an C<eval>, the exception is no
336 longer at risk of being clobbered by code running during unwinding
337 (e.g., destructors). Previously, the exception was written into C<$@>
338 early in the throwing process, and would be overwritten if C<eval> was
339 used internally in the destructor for an object that had to be freed
340 while exiting from the outer C<eval>. Now the exception is written
341 into C<$@> last thing before exiting the outer C<eval>, so the code
342 running immediately thereafter can rely on the value in C<$@> correctly
343 corresponding to that C<eval>. (C<$@> is still also set before exiting the
344 C<eval>, for the sake of destructors that rely on this.)
346 Likewise, a C<local $@> inside an C<eval> will no longer clobber any
347 exception thrown in its scope. Previously, the restoration of C<$@> upon
348 unwinding would overwrite any exception being thrown. Now the exception
349 gets to the C<eval> anyway. So C<local $@> is safe before a C<die>.
351 Exceptions thrown from object destructors no longer modify the C<$@>
352 of the surrounding context. (If the surrounding context was exception
353 unwinding, this used to be another way to clobber the exception being
354 thrown.) Previously such an exception was
355 sometimes emitted as a warning, and then either was
356 string-appended to the surrounding C<$@> or completely replaced the
357 surrounding C<$@>, depending on whether that exception and the surrounding
358 C<$@> were strings or objects. Now, an exception in this situation is
359 always emitted as a warning, leaving the surrounding C<$@> untouched.
360 In addition to object destructors, this also affects any function call
361 performed by XS code using the C<G_KEEPERR> flag.
363 Warnings for C<warn> can now be objects, in the same way as exceptions
364 for C<die>. If an object-based warning gets the default handling,
365 of writing to standard error, it is stringified as
366 before, with the file and line number appended. But
367 a C<$SIG{__WARN__}> handler will now receive an
368 object-based warning as an object, where previously it was passed the
369 result of stringifying the object.
371 =head2 Other Enhancements
373 =head3 Assignment to C<$0> sets the legacy process name with C<prctl()> on Linux
375 On Linux the legacy process name is now set with L<prctl(2)>, in
376 addition to altering the POSIX name via C<argv[0]> as perl has done
377 since version 4.000. Now system utilities that read the legacy process
378 name such as ps, top and killall will recognize the name you set when
379 assigning to C<$0>. The string you supply will be cut off at 16 bytes;
380 this is a limitation imposed by Linux.
382 =head3 C<srand()> now returns the seed
384 This allows programs that need to have repeatable results not to have to come
385 up with their own seed-generating mechanism. Instead, they can use C<srand()>
386 and stash the return value for future use. Typical is a test program which
387 has too many combinations to test comprehensively in the time available to it
388 each run. It can test a random subset each time and, should there be a failure,
389 log the seed used for that run so that it can later be used to reproduce the
392 =head3 printf-like functions understand post-1980 size modifiers
394 Perl's printf and sprintf operators, and Perl's internal printf replacement
395 function, now understand the C90 size modifiers "hh" (C<char>), "z"
396 (C<size_t>), and "t" (C<ptrdiff_t>). Also, when compiled with a C99
397 compiler, Perl now understands the size modifier "j" (C<intmax_t>).
399 So, for example, on any modern machine, C<sprintf('%hhd', 257)> returns '1'.
401 =head3 New global variable C<${^GLOBAL_PHASE}>
403 A new global variable, C<${^GLOBAL_PHASE}>, has been added to allow
404 introspection of the current phase of the perl interpreter. It's explained in
405 detail in L<perlvar/"${^GLOBAL_PHASE}"> and
406 L<perlmod/"BEGIN, UNITCHECK, CHECK, INIT and END">.
408 =head3 C<-d:-foo> calls C<Devel::foo::unimport>
410 The syntax C<-dI<B<:>foo>> was extended in 5.6.1 to make C<-dI<:fooB<=bar>>>
411 equivalent to C<-MDevel::foo=bar>, which expands
412 internally to C<use Devel::foo 'bar';>.
413 F<perl> now allows prefixing the module name with C<->, with the same
414 semantics as C<-M>, I<i.e.>
420 Equivalent to C<-M-Devel::foo>, expands to
421 C<no Devel::foo;>, calls C<< Devel::foo->unimport() >>
422 if the method exists.
426 Equivalent to C<-M-Devel::foo=bar>, expands to C<no Devel::foo 'bar';>,
427 calls C<< Devel::foo->unimport('bar') >> if the method exists.
431 This is particularly useful for suppressing the default actions of a
432 C<Devel::*> module's C<import> method whilst still loading it for debugging.
434 =head3 Filehandle method calls load L<IO::File> on demand
436 When a method call on a filehandle would die because the method cannot
437 be resolved, and L<IO::File> has not been loaded, Perl now loads L<IO::File>
438 via C<require> and attempts method resolution again:
440 open my $fh, ">", $file;
441 $fh->binmode(":raw"); # loads IO::File and succeeds
443 This also works for globs like STDOUT, STDERR and STDIN:
445 STDOUT->autoflush(1);
447 Because this on-demand load only happens if method resolution fails, the
448 legacy approach of manually loading an L<IO::File> parent class for partial
449 method support still works as expected:
452 open my $fh, ">", $file;
453 $fh->autoflush(1); # IO::File not loaded
457 The C<Socket> module provides new affordances for IPv6,
458 including implementations of the C<Socket::getaddrinfo()> and
459 C<Socket::getnameinfo()> functions, along with related constants, and a
460 handful of new functions. See L<Socket>.
462 =head3 DTrace probes now include package name
464 The DTrace probes now include an additional argument (C<arg3>) which contains
465 the package the subroutine being entered or left was compiled in.
467 For example using the following DTrace script:
469 perl$target:::sub-entry
471 printf("%s::%s\n", copyinstr(arg0), copyinstr(arg3));
476 perl -e'sub test { }; test'
484 See L</Internal Changes>.
488 =head2 User-defined regular expression properties
490 In L<perlunicode/"User-Defined Character Properties">, it says you can
491 create custom properties by defining subroutines whose names begin with
492 "In" or "Is". However, Perl did not actually enforce that naming
493 restriction, so \p{foo::bar} could call foo::bar() if it existed. Now this
494 convention has been enforced.
496 Also, Perl no longer allows a tainted regular expression to invoke a
497 user-defined property. It simply dies instead [perl #82616].
499 =head1 Incompatible Changes
501 Perl 5.14.0 is not binary-compatible with any previous stable release.
503 In addition to the sections that follow, see L</C API Changes>.
505 =head2 Regular Expressions and String Escapes
509 Use of C<\400>-C<\777> in regexes in certain circumstances has given
510 different, anomalous behavior than their use in all other
511 double-quote-like contexts. Since 5.10.1, a deprecated warning message
512 has been raised when this happens. Now, all double-quote-like contexts
513 have the same behavior, namely to be equivalent to C<\x{100}> -
514 C<\x{1FF}>, with no deprecation warning. Use of these values in the
515 command line option C<"-0"> retains the current meaning to slurp input
516 files whole; previously, this was documented only for C<"-0777">. It is
517 recommended, however, because of various ambiguities, to use the new
518 C<\o{...}> construct to represent characters in octal.
520 =head3 Most C<\p{}> properties are now immune to case-insensitive matching
522 For most Unicode properties, it doesn't make sense to have them match
523 differently under C</i> case-insensitive matching than not. And doing
524 so leads to unexpected results and potential security holes. For
527 m/\p{ASCII_Hex_Digit}+/i
529 could previously match non-ASCII characters because of the Unicode
530 matching rules (although there were a number of bugs with this). Now
531 matching under C</i> gives the same results as non-C</i> matching except
532 for those few properties where people have come to expect differences,
533 namely the ones where casing is an integral part of their meaning, such
534 as C<m/\p{Uppercase}/i> and C<m/\p{Lowercase}/i>, both of which match
535 the exact same code points, namely those matched by C<m/\p{Cased}/i>.
536 Details are in L<perlrecharclass/Unicode Properties>.
538 User-defined property handlers that need to match differently under
539 C</i> must change to read the new boolean parameter passed to them which is
540 non-zero if case-insensitive matching is in effect or 0 otherwise. See
541 L<perluniprops/User-Defined Character Properties>.
543 =head3 \p{} implies Unicode semantics
545 Now, a Unicode property match specified in the pattern will indicate
546 that the pattern is meant for matching according to Unicode rules, the way
549 =head3 Regular expressions retain their localeness when interpolated
551 Regular expressions compiled under C<"use locale"> now retain this when
552 interpolated into a new regular expression compiled outside a
553 C<"use locale">, and vice-versa.
555 Previously, a regular expression interpolated into another one inherited
556 the localeness of the surrounding one, losing whatever state it
557 originally had. This is considered a bug fix, but may trip up code that
558 has come to rely on the incorrect behavior.
560 =head3 Stringification of regexes has changed
562 Default regular expression modifiers are now notated by using
563 C<(?^...)>. Code relying on the old stringification will fail. The
564 purpose of this is so that when new modifiers are added, such code will
565 not have to change (after this one time), as the stringification will
566 automatically incorporate the new modifiers.
568 Code that needs to work properly with both old- and new-style regexes
569 can avoid the whole issue by using (for Perls since 5.9.5; see L<re>):
571 use re qw(regexp_pattern);
572 my ($pat, $mods) = regexp_pattern($re_ref);
574 If the actual stringification is important, or older Perls need to be
575 supported, you can use something like the following:
577 # Accept both old and new-style stringification
578 my $modifiers = (qr/foobar/ =~ /\Q(?^/) ? '^' : '-xism';
580 And then use C<$modifiers> instead of C<-xism>.
582 =head3 Run-time code blocks in regular expressions inherit pragmata
584 Code blocks in regular expressions (C<(?{...})> and C<(??{...})>) used not
585 to inherit any pragmata (strict, warnings, etc.) if the regular expression
586 was compiled at run time as happens in cases like these two:
589 $foo =~ $bar; # when $bar contains (?{...})
590 $foo =~ /$bar(?{ $finished = 1 })/;
592 This was a bug, which has now been fixed. But
593 it has the potential to break
594 any code that was relying on it.
596 =head2 Stashes and Package Variables
598 =head3 Localised tied hashes and arrays are no longed tied
605 # here, @a is a now a new, untied array
607 # here, @a refers again to the old, tied array
609 The new local array used to be made tied too, which was fairly pointless,
610 and has now been fixed. This fix could however potentially cause a change
611 in behaviour of some code.
613 =head3 Stashes are now always defined
615 C<defined %Foo::> now always returns true, even when no symbols have yet been
616 defined in that package.
618 This is a side effect of removing a special case kludge in the tokeniser,
619 added for 5.10.0, to hide side effects of changes to the internal storage of
620 hashes that drastically reduce their memory usage overhead.
622 Calling defined on a stash has been deprecated since 5.6.0, warned on
623 lexicals since 5.6.0, and warned for stashes (and other package
624 variables) since 5.12.0. C<defined %hash> has always exposed an
625 implementation detail - emptying a hash by deleting all entries from it does
626 not make C<defined %hash> false, hence C<defined %hash> is not valid code to
627 determine whether an arbitrary hash is empty. Instead, use the behaviour
628 that an empty C<%hash> always returns false in a scalar context.
630 =head3 Clearing stashes
632 Stash list assignment C<%foo:: = ()> used to make the stash anonymous
633 temporarily while it was being emptied. Consequently, any of its
634 subroutines referenced elsewhere would become anonymous (showing up as
635 "(unknown)" in C<caller>). Now they retain their package names, such that
636 C<caller> will return the original sub name if there is still a reference
637 to its typeglob, or "foo::__ANON__" otherwise [perl #79208].
639 =head3 Dereferencing typeglobs
641 If you assign a typeglob to a scalar variable:
645 the glob that is copied to C<$glob> is marked with a special flag
646 indicating that the glob is just a copy. This
647 allows subsequent assignments to C<$glob> to
648 overwrite the glob. The original glob, however, is
651 Some Perl operators did not distinguish between these two types of globs.
652 This would result in strange behaviour in edge cases: C<untie $scalar>
653 would not untie the scalar if the last thing assigned to it was a glob
654 (because it treated it as C<untie *$scalar>, which unties a handle).
655 Assignment to a glob slot (e.g., C<*$glob = \@some_array>) would simply
656 assign C<\@some_array> to C<$glob>.
658 To fix this, the C<*{}> operator (including the C<*foo> and C<*$foo> forms)
659 has been modified to make a new immutable glob if its operand is a glob
660 copy. This allows operators that make a distinction between globs and
661 scalars to be modified to treat only immutable globs as globs. (C<tie>,
662 C<tied> and C<untie> have been left as they are for compatibility's sake,
663 but will warn. See L</Deprecations>.)
665 This causes an incompatible change in code that assigns a glob to the
666 return value of C<*{}> when that operator was passed a glob copy. Take the
667 following code, for instance:
672 The C<*$glob> on the second line returns a new immutable glob. That new
673 glob is made an alias to C<*bar>. Then it is discarded. So the second
674 assignment has no effect.
676 See L<http://rt.perl.org/rt3/Public/Bug/Display.html?id=77810> for even
679 =head3 Magic variables outside the main package
681 In previous versions of Perl, magic variables like C<$!>, C<%SIG>, etc. would
682 'leak' into other packages. So C<%foo::SIG> could be used to access signals,
683 C<${"foo::!"}> (with strict mode off) to access C's C<errno>, etc.
685 This was a bug, or an 'unintentional' feature, which caused various ill effects,
686 such as signal handlers being wiped when modules were loaded, etc.
688 This has been fixed (or the feature has been removed, depending on how you see
691 =head3 local($_) will strip all magic from $_
693 local() on scalar variables will give them a new value, but keep all
694 their magic intact. This has proven to be problematic for the default
695 scalar variable $_, where L<perlsub> recommends that any subroutine
696 that assigns to $_ should localize it first. This would throw an
697 exception if $_ is aliased to a read-only variable, and could have
698 various unintentional side-effects in general.
700 Therefore, as an exception to the general rule, local($_) will not
701 only assign a new value to $_, but also remove all existing magic from
704 =head2 Changes to Syntax or to Perl Operators
706 =head3 C<given> return values
708 C<given> blocks now return the last evaluated
709 expression, or an empty list if the block was exited by C<break>. Thus you
715 'integer' when /^[+-]?[0-9]+$/;
716 'float' when /^[+-]?[0-9]+(?:\.[0-9]+)?$/;
721 See L<perlsyn/Return value> for details.
723 =head3 Change in the parsing of certain prototypes
725 Functions declared with the following prototypes now behave correctly as unary
735 Due to this bug fix [perl #75904], functions
736 using the C<(*)>, C<(;$)> and C<(;*)> prototypes
737 are parsed with higher precedence than before. So
738 in the following example:
743 the second line is now parsed correctly as C<< foo($a) < $b >>, rather than
744 C<< foo($a < $b) >>. This happens when one of these operators is used in
745 an unparenthesised argument:
747 < > <= >= lt gt le ge
748 == != <=> eq ne cmp ~~
757 =head3 Smart-matching against array slices
759 Previously, the following code resulted in a successful match:
765 This odd behaviour has now been fixed [perl #77468].
767 =head3 Negation treats strings differently from before
769 The unary negation operator C<-> now treats strings that look like numbers
770 as numbers [perl #57706].
774 Negative zero (-0.0), when converted to a string, now becomes "0" on all
775 platforms. It used to become "-0" on some, but "0" on others.
777 If you still need to determine whether a zero is negative, use
778 C<sprintf("%g", $zero) =~ /^-/> or the L<Data::Float> module on CPAN.
780 =head3 C<:=> is now a syntax error
782 Previously C<my $pi := 4;> was exactly equivalent to C<my $pi : = 4;>,
783 with the C<:> being treated as the start of an attribute list, ending before
784 the C<=>. The use of C<:=> to mean C<: => was deprecated in 5.12.0, and is
785 now a syntax error. This will allow the future use of C<:=> as a new
788 We find no Perl 5 code on CPAN using this construction, outside the core's
789 tests for it, so we believe that this change will have very little impact on
790 real-world codebases.
792 If it is absolutely necessary to have empty attribute lists (for example,
793 because of a code generator) then avoid the error by adding a space before
796 =head2 Threads and Processes
798 =head3 Directory handles not copied to threads
800 On systems other than Windows that do not have
801 a C<fchdir> function, newly-created threads no
802 longer inherit directory handles from their parent threads. Such programs
803 would usually have crashed anyway [perl #75154].
805 =head3 C<close> on shared pipes
807 The C<close> function no longer waits for the child process to exit if the
808 underlying file descriptor is still in use by another thread, to avoid
809 deadlocks. It returns true in such cases.
811 =head3 fork() emulation will not wait for signalled children
813 On Windows parent processes would not terminate until all forked
814 childred had terminated first. However, C<kill('KILL', ...)> is
815 inherently unstable on pseudo-processes, and C<kill('TERM', ...)>
816 might not get delivered if the child is blocked in a system call.
818 To avoid the deadlock and still provide a safe mechanism to terminate
819 the hosting process, Perl will now no longer wait for children that
820 have been sent a SIGTERM signal. It is up to the parent process to
821 waitpid() for these children if child clean-up processing must be
822 allowed to finish. However, it is also the responsibility of the
823 parent then to avoid the deadlock by making sure the child process
824 can't be blocked on I/O either.
826 See L<perlfork> for more information about the fork() emulation on
831 =head3 Naming fixes in Policy_sh.SH may invalidate Policy.sh
833 Several long-standing typos and naming confusions in Policy_sh.SH have
834 been fixed, standardizing on the variable names used in config.sh.
836 This will change the behavior of Policy.sh if you happen to have been
837 accidentally relying on its incorrect behavior.
839 =head3 Perl source code is read in text mode on Windows
841 Perl scripts used to be read in binary mode on Windows for the benefit
842 of the ByteLoader module (which is no longer part of core Perl). This
843 had the side effect of breaking various operations on the DATA filehandle,
844 including seek()/tell(), and even simply reading from DATA after file handles
845 have been flushed by a call to system(), backticks, fork() etc.
847 The default build options for Windows have been changed to read Perl source
848 code on Windows in text mode now. Hopefully ByteLoader will be updated on
849 CPAN to automatically handle this situation [perl #28106].
853 See also L</Deprecated C APIs>.
855 =head2 Omitting a space between a regular expression and subsequent word
857 Omitting a space between a regular expression operator or
858 its modifiers and the following word is deprecated. For
859 example, C<< m/foo/sand $bar >> will still be parsed
860 as C<< m/foo/s and $bar >> but will issue a warning.
864 The backslash-c construct was designed as a way of specifying
865 non-printable characters, but there were no restrictions (on ASCII
866 platforms) on what the character following the C<c> could be. Now,
867 a deprecation warning is raised if that character isn't an ASCII character.
868 Also, a deprecation warning is raised for C<"\c{"> (which is the same
869 as simply saying C<";">).
871 =head2 C<"\b{"> and C<"\B{">
873 In regular expressions, a literal C<"{"> immediately following a C<"\b">
874 (not in a bracketed character class) or a C<"\B{"> is now deprecated
875 to allow for its future use by Perl itself.
877 =head2 Deprecation warning added for deprecated-in-core .pl libs
879 This is a mandatory warning, not obeying -X or lexical warning bits.
880 The warning is modelled on that supplied by deprecate.pm for
881 deprecated-in-core .pm libraries. It points to the specific CPAN
882 distribution that contains the .pl libraries. The CPAN version, of
883 course, does not generate the warning.
885 =head2 List assignment to C<$[>
887 Assignment to C<$[> was deprecated and started to give warnings in
888 Perl version 5.12.0. This version of perl also starts to emit a warning when
889 assigning to C<$[> in list context. This fixes an oversight in 5.12.0.
891 =head2 Use of qw(...) as parentheses
893 Historically the parser fooled itself into thinking that C<qw(...)> literals
894 were always enclosed in parentheses, and as a result you could sometimes omit
895 parentheses around them:
897 for $x qw(a b c) { ... }
899 The parser no longer lies to itself in this way. Wrap the list literal in
900 parentheses, like this:
902 for $x (qw(a b c)) { ... }
904 =head2 C<\N{BELL}> is deprecated
906 This is because Unicode is using that name for a different character.
907 See L</Unicode Version 6.0 is now supported (mostly)> for more
910 =head2 C<?PATTERN?> is deprecated
912 C<?PATTERN?> (without the initial m) has been deprecated and now produces
913 a warning. This is to allow future use of C<?> in new operators.
914 The match-once functionality is still available in the form of C<m?PATTERN?>.
916 =head2 Tie functions on scalars holding typeglobs
918 Calling a tie function (C<tie>, C<tied>, C<untie>) with a scalar argument
919 acts on a file handle if the scalar happens to hold a typeglob.
921 This is a long-standing bug that will be removed in Perl 5.16, as
922 there is currently no way to tie the scalar itself when it holds
923 a typeglob, and no way to untie a scalar that has had a typeglob
926 Now there is a deprecation warning whenever a tie
927 function is used on a handle without an explicit C<*>.
929 =head2 User-defined case-mapping
931 This feature is being deprecated due to its many issues, as documented in
932 L<perlunicode/User-Defined Case Mappings (for serious hackers only)>.
933 It is planned to remove this feature in Perl 5.16. Instead use the CPAN module
934 L<Unicode::Casing>, which provides improved functionality.
936 =head2 Deprecated modules
938 The following modules will be removed from the core distribution in a
939 future release, and should be installed from CPAN instead. Distributions
940 on CPAN which require these should add them to their prerequisites. The
941 core versions of these modules will issue a deprecation warning.
943 If you ship a packaged version of Perl, either alone or as part of a
944 larger system, then you should carefully consider the repercussions of
945 core module deprecations. You may want to consider shipping your default
946 build of Perl with packages for some or all deprecated modules which
947 install into C<vendor> or C<site> perl library directories. This will
948 inhibit the deprecation warnings.
950 Alternatively, you may want to consider patching F<lib/deprecate.pm>
951 to provide deprecation warnings specific to your packaging system
952 or distribution of Perl, consistent with how your packaging system
953 or distribution manages a staged transition from a release where the
954 installation of a single package provides the given functionality, to
955 a later release where the system administrator needs to know to install
956 multiple packages to get that same functionality.
958 You can silence these deprecation warnings by installing the modules
959 in question from CPAN. To install the latest version of all of them,
960 just install C<Task::Deprecations::5_14>.
964 =item L<Devel::DProf>
966 We strongly recommend that you install and used L<Devel::NYTProf> in
967 preference, as it offers significantly improved profiling and reporting.
971 =head1 Performance Enhancements
973 =head2 "Safe signals" optimisation
975 Signal dispatch has been moved from the runloop into control ops. This
976 should give a few percent speed increase, and eliminates almost all of
977 the speed penalty caused by the introduction of "safe signals" in
978 5.8.0. Signals should still be dispatched within the same statement as
979 they were previously - if this is not the case, or it is possible to
980 create uninterruptible loops, this is a bug, and reports are encouraged
981 of how to recreate such issues.
983 =head2 Optimisation of shift; and pop; calls without arguments
985 Two fewer OPs are used for shift and pop calls with no argument (with
986 implicit C<@_>). This change makes C<shift;> 5% faster than C<shift @_;>
987 on non-threaded perls and 25% faster on threaded.
989 =head2 Optimisation of regexp engine string comparison work
991 The foldEQ_utf8 API function for case-insensitive comparison of strings (which
992 is used heavily by the regexp engine) was substantially refactored and
993 optimised - and its documentation much improved as a free bonus gift.
995 =head2 Regular expression compilation speed-up
997 Compiling regular expressions has been made faster for the case where upgrading
998 the regex to utf8 is necessary but that isn't known when the compilation begins.
1000 =head2 String appending is 100 times faster
1002 When doing a lot of string appending, perl could end up allocating a lot more
1003 memory than needed in a very inefficient way, if perl was configured to use the
1004 system's C<malloc> implementation instead of its own.
1006 C<sv_grow>, which is what's being used to allocate more memory if necessary
1007 when appending to a string, has now been taught how to round up the memory
1008 it requests to a certain geometric progression, making it much faster on
1009 certain platforms and configurations. On Win32, it's now about 100 times
1012 =head2 Eliminate C<PL_*> accessor functions under ithreads
1014 When C<MULTIPLICITY> was first developed, and interpreter state moved into
1015 an interpreter struct, thread and interpreter local C<PL_*> variables were
1016 defined as macros that called accessor functions, returning the address of
1017 the value, outside of the perl core. The intent was to allow members
1018 within the interpreter struct to change size without breaking binary
1019 compatibility, so that bug fixes could be merged to a maintenance branch
1020 that necessitated such a size change.
1022 However, some non-core code defines C<PERL_CORE>, sometimes intentionally
1023 to bypass this mechanism for speed reasons, sometimes for other reasons but
1024 with the inadvertent side effect of bypassing this mechanism. As some of
1025 this code is widespread in production use, the result is that the core
1026 I<can't> change the size of members of the interpreter struct, as it will
1027 break such modules compiled against a previous release on that maintenance
1028 branch. The upshot is that this mechanism is redundant, and well-behaved
1029 code is penalised by it. Hence it can and should be removed (and has
1032 =head2 Freeing weak references
1034 When an object has many weak references to it, freeing that object
1035 can under some some circumstances take O(N^2) time to free (where N is the
1036 number of references). The number of circumstances has been reduced
1039 =head2 Lexical array and hash assignments
1041 An earlier optimisation to speed up C<my @array = ...> and
1042 C<my %hash = ...> assignments caused a bug and was disabled in Perl 5.12.0.
1044 Now we have found another way to speed up these assignments [perl #82110].
1046 =head2 C<@_> uses less memory
1048 Previously, C<@_> was allocated for every subroutine at compile time with
1049 enough space for four entries. Now this allocation is done on demand when
1050 the subroutine is called [perl #72416].
1052 =head2 Size optimisations to SV and HV structures
1054 xhv_fill has been eliminated from struct xpvhv, saving 1 IV per hash and
1055 on some systems will cause struct xpvhv to become cache-aligned. To avoid
1056 this memory saving causing a slowdown elsewhere, boolean use of HvFILL
1057 now calls HvTOTALKEYS instead (which is equivalent) - so while the fill
1058 data when actually required are now calculated on demand, the cases when
1059 this needs to be done should be few and far between.
1061 The order of structure elements in SV bodies has changed. Effectively,
1062 the NV slot has swapped location with STASH and MAGIC. As all access to
1063 SV members is via macros, this should be completely transparent. This
1064 change allows the space saving for PVHVs documented above, and may reduce
1065 the memory allocation needed for PVIVs on some architectures.
1067 C<XPV>, C<XPVIV>, and C<XPVNV> now only allocate the parts of the C<SV> body
1068 they actually use, saving some space.
1070 Scalars containing regular expressions now only allocate the part of the C<SV>
1071 body they actually use, saving some space.
1073 =head2 Memory consumption improvements to Exporter
1075 The @EXPORT_FAIL AV is no longer created unless required, hence neither is
1076 the typeglob backing it. This saves about 200 bytes for every package that
1077 uses Exporter but doesn't use this functionality.
1079 =head2 Memory savings for weak references
1081 For weak references, the common case of just a single weak reference per
1082 referent has been optimised to reduce the
1083 storage required. In this case it
1084 saves the equivalent of one small Perl array per referent.
1086 =head2 C<%+> and C<%-> use less memory
1088 The bulk of the C<Tie::Hash::NamedCapture> module used to be in the perl
1089 core. It has now been moved to an XS module, to reduce the overhead for
1090 programs that do not use C<%+> or C<%->.
1092 =head2 Multiple small improvements to threads
1094 The internal structures of threading now make fewer API calls and fewer
1095 allocations, resulting in noticeably smaller object code. Additionally,
1096 many thread context checks have been deferred so that they're only done
1097 when required (although this is only possible for non-debugging builds).
1099 =head2 Adjacent pairs of nextstate opcodes are now optimized away
1101 Previously, in code such as
1103 use constant DEBUG => 0;
1110 the ops for C<warn if DEBUG;> would be folded to a C<null> op (C<ex-const>), but
1111 the C<nextstate> op would remain, resulting in a runtime op dispatch of
1112 C<nextstate>, C<nextstate>, ....
1114 The execution of a sequence of C<nextstate> ops is indistinguishable from just
1115 the last C<nextstate> op so the peephole optimizer now eliminates the first of
1116 a pair of C<nextstate> ops, except where the first carries a label, since labels
1117 must not be eliminated by the optimizer and label usage isn't conclusively known
1120 =head1 Modules and Pragmata
1122 =head2 New Modules and Pragmata
1128 C<CPAN::Meta::YAML> 0.003 has been added as a dual-life module. It supports a
1129 subset of YAML sufficient for reading and writing META.yml and MYMETA.yml files
1130 included with CPAN distributions or generated by the module installation
1131 toolchain. It should not be used for any other general YAML parsing or
1136 C<CPAN::Meta> version 2.110440 has been added as a dual-life module. It
1137 provides a standard library to read, interpret and write CPAN distribution
1138 metadata files (e.g. META.json and META.yml) which describes a
1139 distribution, its contents, and the requirements for building it and
1140 installing it. The latest CPAN distribution metadata specification is
1141 included as C<CPAN::Meta::Spec> and notes on changes in the specification
1142 over time are given in C<CPAN::Meta::History>.
1146 C<HTTP::Tiny> 0.012 has been added as a dual-life module. It is a very
1147 small, simple HTTP/1.1 client designed for simple GET requests and file
1148 mirroring. It has has been added to enable CPAN.pm and CPANPLUS to
1149 "bootstrap" HTTP access to CPAN using pure Perl without relying on external
1150 binaries like F<curl> or F<wget>.
1154 C<JSON::PP> 2.27105 has been added as a dual-life module, for the sake of
1155 reading F<META.json> files in CPAN distributions.
1159 C<Module::Metadata> 1.000004 has been added as a dual-life module. It gathers
1160 package and POD information from Perl module files. It is a standalone module
1161 based on Module::Build::ModuleInfo for use by other module installation
1162 toolchain components. Module::Build::ModuleInfo has been deprecated in
1163 favor of this module instead.
1167 C<Perl::OSType> 1.002 has been added as a dual-life module. It maps Perl
1168 operating system names (e.g. 'dragonfly' or 'MSWin32') to more generic types
1169 with standardized names (e.g. "Unix" or "Windows"). It has been refactored
1170 out of Module::Build and ExtUtils::CBuilder and consolidates such mappings into
1171 a single location for easier maintenance.
1175 The following modules were added by the C<Unicode::Collate>
1176 upgrade. See below for details.
1178 C<Unicode::Collate::CJK::Big5>
1180 C<Unicode::Collate::CJK::GB2312>
1182 C<Unicode::Collate::CJK::JISX0208>
1184 C<Unicode::Collate::CJK::Korean>
1186 C<Unicode::Collate::CJK::Pinyin>
1188 C<Unicode::Collate::CJK::Stroke>
1192 C<Version::Requirements> version 0.101020 has been added as a dual-life
1193 module. It provides a standard library to model and manipulates module
1194 prerequisites and version constraints as defined in the L<CPAN::Meta::Spec>.
1198 =head2 Updated Modules and Pragma
1204 C<attributes> has been upgraded from version 0.12 to 0.14.
1208 C<Archive::Extract> has been upgraded from version 0.38 to 0.48.
1210 Updates since 0.38 include: a safe print method that guards
1211 Archive::Extract from changes to $\; a fix to the tests when run in core
1212 perl; support for TZ files; a modification for the lzma
1213 logic to favour IO::Uncompress::Unlzma; and a fix
1214 for an issue with NetBSD-current and its new unzip
1219 C<Archive::Tar> has been upgraded from version 1.54 to 1.76.
1221 Important changes since 1.54 include the following:
1227 Compatibility with busybox implementations of tar
1231 A fix so that C<write()> and C<create_archive()>
1232 close only handles they opened
1236 A bug was fixed regarding the exit code of extract_archive.
1240 The C<ptar> utility has a new option to allow safe
1241 creation of tarballs without world-writable files on Windows, allowing those
1242 archives to be uploaded to CPAN.
1246 A new ptargrep utility for using regular expressions against
1247 the contents of files in a tar archive.
1251 Pax extended headers are now skipped.
1257 C<Attribute::Handlers> has been upgraded from version 0.87 to 0.89.
1261 C<autodie> has been upgraded from version 2.06_01 to 2.1001.
1265 C<AutoLoader> has been upgraded from version 5.70 to 5.71.
1269 C<B> has been upgraded from version 1.23 to 1.29.
1271 It no longer crashes when taking apart a C<y///> containing characters
1272 outside the octet range or compiled in a C<use utf8> scope.
1274 The size of the shared object has been reduced by about 40%, with no
1275 reduction in functionality.
1279 C<B::Concise> has been upgraded from version 0.78 to 0.83.
1281 B::Concise marks rv2sv, rv2av and rv2hv ops with the new OPpDEREF flag
1284 It no longer produces mangled output with the C<-tree> option
1289 C<B::Debug> has been upgraded from version 1.12 to 1.16.
1293 C<B::Deparse> has been upgraded from version 0.96 to 1.03.
1295 The deparsing of a nextstate op has changed when it has both a
1296 change of package (relative to the previous nextstate), or a change of
1297 C<%^H> or other state, and a label. Previously the label was emitted
1298 first, but now the label is emitted last (5.12.1).
1300 The C<no 5.13.2> or similar form is now correctly handled by B::Deparse
1303 B::Deparse now properly handles the code that applies a conditional
1304 pattern match against implicit C<$_> as it was fixed in [perl #20444].
1306 Deparsing of C<our> followed by a variable with funny characters
1307 (as permitted under the C<utf8> pragma) has also been fixed [perl #33752].
1311 C<B::Lint> has been upgraded from version 1.11_01 to 1.13.
1315 C<base> has been upgraded from version 2.15 to 2.16.
1319 C<Benchmark> has been upgraded from version 1.11 to 1.12.
1323 C<bignum> has been upgraded from version 0.23 to 0.27.
1327 C<Carp> has been upgraded from version 1.15 to 1.20.
1329 L<Carp> now detects incomplete L<caller()|perlfunc/"caller EXPR"> overrides and
1330 avoids using bogus C<@DB::args>. To provide backtraces,
1331 Carp relies on particular behaviour of the C<caller>
1332 built-in. Carp now detects if other code has
1333 overridden this with an incomplete implementation, and modifies its backtrace
1334 accordingly. Previously incomplete overrides would cause incorrect values
1335 in backtraces (best case), or obscure fatal errors (worst case).
1337 This fixes certain cases of C<Bizarre copy of ARRAY> caused by modules
1338 overriding C<caller()> incorrectly (5.12.2).
1340 It now also avoids using regular expressions that cause perl to
1341 load its Unicode tables, in order to avoid the 'BEGIN not safe after
1342 errors' error that will ensue if there has been a syntax error
1347 C<CGI> has been upgraded from version 3.48 to 3.52.
1349 This provides the following security fixes: the MIME boundary in
1350 multipart_init is now random and the handling of
1351 newlines embedded in header values has been improved.
1355 C<Compress::Raw::Bzip2> has been upgraded from version 2.024 to 2.033.
1357 It has been updated to use bzip2 1.0.6.
1361 C<Compress::Raw::Zlib> has been upgraded from version 2.024 to 2.033.
1365 C<CPAN> has been upgraded from version 1.94_56 to 1.9600.
1371 =item * much less configuration dialog hassle
1373 =item * support for META/MYMETA.json
1375 =item * support for local::lib
1377 =item * support for HTTP::Tiny to reduce the dependency on ftp sites
1379 =item * automatic mirror selection
1381 =item * iron out all known bugs in configure_requires
1383 =item * support for distributions compressed with bzip2
1385 =item * allow Foo/Bar.pm on the commandline to mean Foo::Bar
1391 C<CPANPLUS> has been upgraded from version 0.90 to 0.9103.
1393 A change to F<cpanp-run-perl>
1394 resolves L<RT #55964|http://rt.cpan.org/Public/Bug/Display.html?id=55964>
1395 and L<RT #57106|http://rt.cpan.org/Public/Bug/Display.html?id=57106>, both
1396 of which related to failures to install distributions that use
1397 C<Module::Install::DSL> (5.12.2).
1399 A dependency on Config was not recognised as a
1400 core module dependency. This has been fixed.
1402 CPANPLUS now includes support for META.json and MYMETA.json.
1406 C<CPANPLUS::Dist::Build> has been upgraded from version 0.46 to 0.54.
1410 C<Data::Dumper> has been upgraded from version 2.125 to 2.130_02.
1412 The indentation used to be off when C<$Data::Dumper::Terse> was set. This
1413 has been fixed [perl #73604].
1415 This upgrade also fixes a crash when using custom sort functions that might
1416 cause the stack to change [perl #74170].
1418 C<Dumpxs> no longer crashes with globs returned by C<*$io_ref>
1423 C<DB_File> has been upgraded from version 1.820 to 1.821.
1427 C<DBM_Filter> has been upgraded from version 0.03 to 0.04.
1431 C<Devel::DProf> has been upgraded from version 20080331.00 to 20110228.00.
1433 Merely loading C<Devel::DProf> now no longer triggers profiling to start.
1434 C<use Devel::DProf> and C<perl -d:DProf ...> still behave as before and start
1437 NOTE: C<Devel::DProf> is deprecated and will be removed from a future
1438 version of Perl. We strongly recommend that you install and use
1439 L<Devel::NYTProf> instead, as it offers significantly improved
1440 profiling and reporting.
1444 C<Devel::Peek> has been upgraded from version 1.04 to 1.07.
1448 C<Devel::SelfStubber> has been upgraded from version 1.03 to 1.05.
1452 C<diagnostics> has been upgraded from version 1.19 to 1.22.
1454 It now renders pod links slightly better, and has been taught to find
1455 descriptions for messages that share their descriptions with other
1460 C<Digest::MD5> has been upgraded from version 2.39 to 2.51.
1462 It is now safe to use this module in combination with threads.
1466 C<Digest::SHA> has been upgraded from version 5.47 to 5.61.
1468 C<shasum> now more closely mimics C<sha1sum>/C<md5sum>.
1470 C<Addfile> accepts all POSIX filenames.
1472 New SHA-512/224 and SHA-512/256 transforms (ref. NIST Draft FIPS 180-4
1477 C<DirHandle> has been upgraded from version 1.03 to 1.04.
1481 C<Dumpvalue> has been upgraded from version 1.13 to 1.16.
1485 C<DynaLoader> has been upgraded from version 1.10 to 1.13.
1487 It fixes a buffer overflow when passed a very long file name.
1489 It no longer inherits from AutoLoader; hence it no longer
1490 produces weird error messages for unsuccessful method calls on classes that
1491 inherit from DynaLoader [perl #84358].
1495 C<Encode> has been upgraded from version 2.39 to 2.42.
1497 Now, all 66 Unicode non-characters are treated the same way U+FFFF has
1498 always been treated; in cases when it was disallowed, all 66 are
1499 disallowed; in those cases where it warned, all 66 warn.
1503 C<Env> has been upgraded from version 1.01 to 1.02.
1507 C<Errno> has been upgraded from version 1.11 to 1.13.
1509 The implementation of C<Errno> has been refactored to use about 55% less memory.
1511 On some platforms with unusual header files, like Win32/gcc using mingw64
1512 headers, some constants which weren't actually error numbers have been exposed
1513 by C<Errno>. This has been fixed [perl #77416].
1517 C<Exporter> has been upgraded from version 5.64_01 to 5.64_03.
1519 Exporter no longer overrides C<$SIG{__WARN__}> [perl #74472]
1523 C<ExtUtils::CBuilder> has been upgraded from version 0.27 to 0.280202.
1527 C<ExtUtils::Command> has been upgraded from version 1.16 to 1.17.
1531 C<ExtUtils::Constant> has been upgraded from 0.22 to 0.23.
1533 The C<AUTOLOAD> helper code generated by C<ExtUtils::Constant::ProxySubs>
1534 can now C<croak> for missing constants, or generate a complete C<AUTOLOAD>
1535 subroutine in XS, allowing simplification of many modules that use it
1536 (C<Fcntl>, C<File::Glob>, C<GDBM_File>, C<I18N::Langinfo>, C<POSIX>,
1539 C<ExtUtils::Constant::ProxySubs> can now optionally push the names of all
1540 constants onto the package's C<@EXPORT_OK>.
1544 C<ExtUtils::Install> has been upgraded from version 1.55 to 1.56.
1548 C<ExtUtils::MakeMaker> has been upgraded from version 6.56 to 6.57_05.
1552 C<ExtUtils::Manifest> has been upgraded from version 1.57 to 1.58.
1556 C<ExtUtils::ParseXS> has been upgraded from version 2.21 to 2.2210.
1560 C<Fcntl> has been upgraded from version 1.06 to 1.11.
1564 C<File::Basename> has been upgraded from version 2.78 to 2.82.
1568 C<File::CheckTree> has been upgraded from version 4.4 to 4.41.
1572 C<File::Copy> has been upgraded from version 2.17 to 2.21.
1576 C<File::DosGlob> has been upgraded from version 1.01 to 1.04.
1578 It allows patterns containing literal parentheses (they no longer need to
1579 be escaped). On Windows, it no longer
1580 adds an extra F<./> to the file names
1581 returned when the pattern is a relative glob with a drive specification,
1582 like F<c:*.pl> [perl #71712].
1586 C<File::Fetch> has been upgraded from version 0.24 to 0.32.
1588 C<HTTP::Lite> is now supported for 'http' scheme.
1590 The C<fetch> utility is supported on FreeBSD, NetBSD and
1591 Dragonfly BSD for the C<http> and C<ftp> schemes.
1595 C<File::Find> has been upgraded from version 1.15 to 1.19.
1597 It improves handling of backslashes on Windows, so that paths like
1598 F<c:\dir\/file> are no longer generated [perl #71710].
1602 C<File::Glob> has been upgraded from version 1.07 to 1.12.
1606 C<File::Spec> has been upgraded from version 3.31 to 3.33.
1608 Several portability fixes were made in C<File::Spec::VMS>: a colon is now
1609 recognized as a delimiter in native filespecs; caret-escaped delimiters are
1610 recognized for better handling of extended filespecs; C<catpath()> returns
1611 an empty directory rather than the current directory if the input directory
1612 name is empty; C<abs2rel()> properly handles Unix-style input (5.12.2).
1616 C<File::stat> has been upgraded from 1.02 to 1.05.
1618 The C<-x> and C<-X> file test operators now work correctly under the root
1623 C<Filter::Simple> has been upgraded from version 0.84 to 0.86.
1627 C<GDBM_File> has been upgraded from 1.10 to 1.14.
1629 This fixes a memory leak when DBM filters are used.
1633 C<Hash::Util> has been upgraded from 0.07 to 0.11.
1635 Hash::Util no longer emits spurious "uninitialized" warnings when
1636 recursively locking hashes that have undefined values [perl #74280].
1640 C<Hash::Util::FieldHash> has been upgraded from version 1.04 to 1.09.
1644 C<I18N::Collate> has been upgraded from version 1.01 to 1.02.
1648 C<I18N::Langinfo> has been upgraded from version 0.03 to 0.08.
1650 C<langinfo()> now defaults to using C<$_> if there is no argument given, just
1651 as the documentation has always claimed.
1655 C<I18N::LangTags> has been upgraded from version 0.35 to 0.35_01.
1659 C<if> has been upgraded from version 0.05 to 0.0601.
1663 C<IO> has been upgraded from version 1.25_02 to 1.25_04.
1665 This version of C<IO> includes a new C<IO::Select>, which now allows IO::Handle
1666 objects (and objects in derived classes) to be removed from an IO::Select set
1667 even if the underlying file descriptor is closed or invalid.
1671 C<IPC::Cmd> has been upgraded from version 0.54 to 0.70.
1673 Resolves an issue with splitting Win32 command lines. An argument
1674 consisting of the single character "0" used to be omitted (CPAN RT #62961).
1678 C<IPC::Open3> has been upgraded from 1.05 to 1.09.
1680 C<open3> now produces an error if the C<exec> call fails, allowing this
1681 condition to be distinguished from a child process that exited with a
1682 non-zero status [perl #72016].
1684 The internal C<xclose> routine now knows how to handle file descriptors, as
1685 documented, so duplicating STDIN in a child process using its file
1686 descriptor now works [perl #76474].
1690 C<IPC::SysV> has been upgraded from version 2.01 to 2.03.
1694 C<lib> has been upgraded from version 0.62 to 0.63.
1698 C<Locale::Maketext> has been upgraded from version 1.14 to 1.19.
1700 Locale::Maketext now supports external caches.
1702 This upgrade also fixes an infinite loop in
1703 C<Locale::Maketext::Guts::_compile()> when
1704 working with tainted values (CPAN RT #40727).
1706 C<< ->maketext >> calls will now back up and restore C<$@> so that error
1707 messages are not suppressed (CPAN RT #34182).
1711 C<Log::Message> has been upgraded from version 0.02 to 0.04.
1715 C<Log::Message::Simple> has been upgraded from version 0.06 to 0.08.
1719 C<Math::BigInt> has been upgraded from version 1.89_01 to 1.994.
1721 This fixes, among other things, incorrect results when computing binomial
1722 coefficients [perl #77640].
1724 It also prevents C<sqrt($int)> from crashing under C<use bigrat;>
1729 C<Math::BigInt::FastCalc> has been upgraded from version 0.19 to 0.28.
1733 C<Math::BigRat> has been upgraded from version 0.24 to 0.26_02.
1737 C<Memoize> has been upgraded from version 1.01_03 to 1.02.
1741 C<MIME::Base64> has been upgraded from 3.08 to 3.13.
1743 Includes new functions to calculate the length of encoded and decoded
1746 Now provides C<encode_base64url> and C<decode_base64url> functions to process
1747 the base64 scheme for "URL applications".
1751 C<Module::Build> has been upgraded from version 0.3603 to 0.3800.
1753 A notable change is the deprecation of several modules.
1754 Module::Build::Version has been deprecated and Module::Build now relies
1755 directly upon L<version>. Module::Build::ModuleInfo has been deprecated in
1756 favor of a standalone copy of it called L<Module::Metadata>.
1757 Module::Build::YAML has been deprecated in favor of L<CPAN::Meta::YAML>.
1759 Module::Build now also generates META.json and MYMETA.json files
1760 in accordance with version 2 of the CPAN distribution metadata specification,
1761 L<CPAN::Meta::Spec>. The older format META.yml and MYMETA.yml files are
1762 still generated, as well.
1766 C<Module::CoreList> has been upgraded from version 2.29 to 2.47.
1768 Besides listing the updated core modules of this release, it also stops listing
1769 the C<Filespec> module. That module never existed in core. The scripts
1770 generating C<Module::CoreList> confused it with C<VMS::Filespec>, which actually
1771 is a core module as of perl 5.8.7.
1775 C<Module::Load> has been upgraded from version 0.16 to 0.18.
1779 C<Module::Load::Conditional> has been upgraded from version 0.34 to 0.44.
1783 C<mro> has been upgraded from version 1.02 to 1.07.
1787 C<NDBM_File> has been upgraded from version 1.08 to 1.12.
1789 This fixes a memory leak when DBM filters are used.
1793 C<Net::Ping> has been upgraded from version 2.36 to 2.38.
1797 C<NEXT> has been upgraded from version 0.64 to 0.65.
1801 C<Object::Accessor> has been upgraded from version 0.36 to 0.38.
1805 C<ODBM_File> have been upgraded from version 1.07 to 1.10.
1807 This fixes a memory leak when DBM filters are used.
1811 C<Opcode> has been upgraded from version 1.15 to 1.18.
1815 C<overload> has been upgraded from 1.10 to 1.13.
1817 C<overload::Method> can now handle subroutines that are themselves blessed
1818 into overloaded classes [perl #71998].
1820 The documentation has greatly improved. See L</Documentation> below.
1824 C<Params::Check> has been upgraded from version 0.26 to 0.28.
1828 C<parent> has been upgraded from version 0.223 to 0.225.
1832 C<Parse::CPAN::Meta> has been upgraded from version 1.40 to 1.4401.
1834 The latest Parse::CPAN::Meta can now read YAML and JSON files using
1835 L<CPAN::Meta::YAML> and L<JSON::PP>, which are now part of the Perl core.
1839 C<PerlIO::encoding> has been upgraded from version 0.12 to 0.14.
1843 C<PerlIO::scalar> has been upgraded from 0.07 to 0.11.
1845 A C<read> after a C<seek> beyond the end of the string no longer thinks it
1846 has data to read [perl #78716].
1850 C<PerlIO::via> has been upgraded from version 0.09 to 0.11.
1854 C<Pod::Html> has been upgraded from version 1.09 to 1.11.
1858 C<Pod::LaTeX> has been upgraded from version 0.58 to 0.59.
1862 C<Pod::Perldoc> has been upgraded from version 3.15_02 to 3.15_03.
1866 C<Pod::Simple> has been upgraded from version 3.13 to 3.16.
1870 C<POSIX> has been upgraded from 1.19 to 1.24.
1872 It now includes constants for POSIX signal constants.
1876 C<re> has been upgraded from version 0.11 to 0.17.
1878 New C<use re "/flags"> pragma
1880 The C<regmust> function used to crash when called on a regular expression
1881 belonging to a pluggable engine. Now it croaks instead.
1883 C<regmust> no longer leaks memory.
1887 C<Safe> has been upgraded from version 2.25 to 2.29.
1889 Coderefs returned by C<reval()> and C<rdo()> are now wrapped via
1890 C<wrap_code_refs> (5.12.1).
1892 This fixes a possible infinite loop when looking for coderefs.
1894 It adds several version::vxs::* routines to the default share.
1898 C<SDBM_File> has been upgraded from version 1.06 to 1.09.
1902 C<SelfLoader> has been upgraded from 1.17 to 1.18.
1904 It now works in taint mode [perl #72062].
1908 C<sigtrap> has been upgraded from version 1.04 to 1.05.
1910 It no longer tries to modify read-only arguments when generating a
1911 backtrace [perl #72340].
1915 C<Socket> has been upgraded from version 1.87 to 1.94.
1917 See L</IPv6 support>, above.
1921 C<Storable> has been upgraded from version 2.22 to 2.27.
1923 Includes performance improvement for overloaded classes.
1925 This adds support for serialising code references that contain UTF-8 strings
1926 correctly. The Storable minor version
1927 number changed as a result, meaning that
1928 Storable users who set C<$Storable::accept_future_minor> to a C<FALSE> value
1929 will see errors (see L<Storable/FORWARD COMPATIBILITY> for more details).
1931 Freezing no longer gets confused if the Perl stack gets reallocated
1932 during freezing [perl #80074].
1936 C<Sys::Hostname> has been upgraded from version 1.11 to 1.16.
1940 C<Term::ANSIColor> has been upgraded from version 2.02 to 3.00.
1944 C<Term::UI> has been upgraded from version 0.20 to 0.26.
1948 C<Test::Harness> has been upgraded from version 3.17 to 3.23.
1952 C<Test::Simple> has been upgraded from version 0.94 to 0.98.
1954 Among many other things, subtests without a C<plan> or C<no_plan> now have an
1955 implicit C<done_testing()> added to them.
1959 C<Thread::Semaphore> has been upgraded from version 2.09 to 2.12.
1961 It provides two new methods that give more control over the decrementing of
1962 semaphores: C<down_nb> and C<down_force>.
1966 C<Thread::Queue> has been upgraded from version 2.11 to 2.12.
1970 C<threads> has been upgraded from version 1.75 to 1.83.
1974 C<threads::shared> has been upgraded from version 1.32 to 1.36.
1978 C<Tie::Hash> has been upgraded from version 1.03 to 1.04.
1980 Calling C<< Tie::Hash-E<gt>TIEHASH() >> used to loop forever. Now it C<croak>s.
1984 C<Tie::Hash::NamedCapture> has been upgraded from version 0.06 to 0.08.
1988 C<Tie::RefHash> has been upgraded from version 1.38 to 1.39.
1992 C<Time::HiRes> has been upgraded from version 1.9719 to 1.9721_01.
1996 C<Time::Local> has been upgraded from version 1.1901_01 to 1.2000.
2000 C<Time::Piece> has been upgraded from version 1.15_01 to 1.20_01.
2004 C<Unicode::Collate> has been upgraded from version 0.52_01 to 0.73.
2006 Unicode::Collate has been updated to use Unicode 6.0.0.
2008 Unicode::Collate::Locale now supports a plethora of new locales: ar, be,
2009 bg, de__phonebook, hu, hy, kk, mk, nso, om, tn, vi, hr, ig, ja, ko, ru, sq,
2010 se, sr, to, uk, zh, zh__big5han, zh__gb2312han, zh__pinyin and zh__stroke.
2012 The following modules have been added:
2014 C<Unicode::Collate::CJK::Big5> for C<zh__big5han> which makes
2015 tailoring of CJK Unified Ideographs in the order of CLDR's big5han ordering.
2017 C<Unicode::Collate::CJK::GB2312> for C<zh__gb2312han> which makes
2018 tailoring of CJK Unified Ideographs in the order of CLDR's gb2312han ordering.
2020 C<Unicode::Collate::CJK::JISX0208> which makes tailoring of 6355 kanji
2021 (CJK Unified Ideographs) in the JIS X 0208 order.
2023 C<Unicode::Collate::CJK::Korean> which makes tailoring of CJK Unified Ideographs
2024 in the order of CLDR's Korean ordering.
2026 C<Unicode::Collate::CJK::Pinyin> for C<zh__pinyin> which makes
2027 tailoring of CJK Unified Ideographs in the order of CLDR's pinyin ordering.
2029 C<Unicode::Collate::CJK::Stroke> for C<zh__stroke> which makes
2030 tailoring of CJK Unified Ideographs in the order of CLDR's stroke ordering.
2032 This also sees the switch from using the pure-perl version of this
2033 module to the XS version.
2037 C<Unicode::Normalize> has been upgraded from version 1.03 to 1.10.
2041 C<Unicode::UCD> has been upgraded from version 0.27 to 0.32.
2043 A new function, C<Unicode::UCD::num()>, has been added. This function
2044 returns the numeric value of the string passed it or C<undef> if the string
2045 in its entirety has no "safe" numeric value. (For more detail, and for the
2046 definition of "safe", see L<Unicode::UCD/num>.)
2048 This upgrade also includes a number of bug fixes:
2058 It is now updated to Unicode Version 6 with Corrigendum #8, except,
2059 as with Perl 5.14, the code point at U+1F514 has no name.
2063 The Hangul syllable code points have the correct names, and their
2064 decompositions are always output without requiring L<Lingua::KO::Hangul::Util>
2069 The CJK (Chinese-Japanese-Korean) code points U+2A700 to U+2B734
2070 and U+2B740 to U+2B81D are now properly handled.
2074 The numeric values are now output for those CJK code points that have them.
2078 The names that are output for code points with multiple aliases are now the
2085 This now correctly returns "Unknown" instead of C<undef> for the script
2086 of a code point that hasn't been assigned another one.
2090 This now correctly returns "No_Block" instead of C<undef> for the block
2091 of a code point that hasn't been assigned to another one.
2097 C<version> has been upgraded from 0.82 to 0.88.
2099 Due to a bug, now fixed, the C<is_strict> and C<is_lax> functions did not
2100 work when exported (5.12.1).
2104 C<warnings> has been upgraded from version 1.09 to 1.12.
2106 Calling C<use warnings> without arguments is now significantly more efficient.
2110 C<warnings::register> have been upgraded from version 1.01 to 1.02.
2112 It is now possible to register warning categories other than the names of
2113 packages using C<warnings::register>. See L<perllexwarn> for more information.
2117 C<XSLoader> has been upgraded from version 0.10 to 0.13.
2121 C<VMS::DCLsym> has been upgraded from version 1.03 to 1.05.
2123 Two bugs have been fixed [perl #84086]:
2125 The symbol table name was lost when tying a hash, due to a thinko in
2126 C<TIEHASH>. The result was that all tied hashes interacted with the
2129 Unless a symbol table name had been explicitly specified in the call
2130 to the constructor, querying the special key ':LOCAL' failed to
2131 identify objects connected to the local symbol table.
2135 C<Win32> has been upgraded from version 0.39 to 0.44.
2137 This release has several new functions: C<Win32::GetSystemMetrics>,
2138 C<Win32::GetProductInfo>, C<Win32::GetOSDisplayName>.
2140 The names returned by C<Win32::GetOSName> and C<Win32::GetOSDisplayName>
2141 have been corrected.
2145 C<XS::Typemap> has been upgraded from version 0.03 to 0.05.
2149 =head2 Removed Modules and Pragmata
2151 The following modules have been removed from the core distribution, and if
2152 needed should be installed from CPAN instead.
2158 C<Class::ISA> has been removed from the Perl core. Prior version was 0.36.
2162 C<Pod::Plainer> has been removed from the Perl core. Prior version was 1.02.
2166 C<Switch> has been removed from the Perl core. Prior version was 2.16.
2170 The removal of C<Shell> has been deferred until after 5.14, as the
2171 implementation of C<Shell> shipped with 5.12.0 did not correctly issue the
2172 warning that it was to be removed from core.
2174 =head1 Documentation
2176 =head2 New Documentation
2180 L<perlgpl> has been updated to contain GPL version 1, as is included in the
2181 F<README> distributed with perl (5.12.1).
2183 =head3 Perl 5.12.x delta files
2185 The perldelta files for Perl 5.12.1 to 5.12.3 have been added from the
2186 maintenance branch: L<perl5121delta>, L<perl5122delta>, L<perl5123delta>.
2188 =head3 L<perlpodstyle>
2190 New style guide for POD documentation,
2191 split mostly from the NOTES section of the pod2man man page.
2193 =head3 L<perlsource>, L<perlinterp>, L<perlhacktut>, and L<perlhacktips>
2195 See L</perlhack and perlrepository revamp>, below.
2197 =head2 Changes to Existing Documentation
2199 =head3 L<perlmodlib> is now complete
2201 The perlmodlib page that came with Perl 5.12.0 was missing a lot of
2202 modules, due to a bug in the script that generates the list. This has been
2203 fixed [perl #74332] (5.12.1).
2205 =head3 Replace wrong tr/// table in L<perlebcdic>
2207 L<perlebcdic> contains a helpful table to use in tr/// to convert
2208 between EBCDIC and Latin1/ASCII. Unfortunately, the table was the
2209 inverse of the one it describes, though the code that used the table
2210 worked correctly for the specific example given.
2212 The table has been changed to its inverse, and the sample code changed
2213 to correspond, as this is easier for the person trying to follow the
2214 instructions since deriving the old table is somewhat more complicated.
2216 The table has also been changed to hex from octal, as that is more the norm
2217 these days, and the recipes in the pod altered to print out leading
2218 zeros to make all the values the same length.
2220 =head3 Tricks for user-defined casing
2222 L<perlunicode> now contains an explanation of how to override, mangle
2223 and otherwise tweak the way perl handles upper-, lower- and other-case
2224 conversions on Unicode data, and how to provide scoped changes to alter
2225 one's own code's behaviour without stomping on anybody else.
2227 =head3 INSTALL explicitly states the requirement for C89
2229 This was already true but it's now Officially Stated For The Record
2232 =head3 Explanation of C<\xI<HH>> and C<\oI<OOO>> escapes
2234 L<perlop> has been updated with more detailed explanation of these two
2237 =head3 C<-0I<NNN>> switch
2239 In L<perlrun>, the behavior of the C<-0NNN> switch for C<-0400> or higher
2240 has been clarified (5.12.2).
2242 =head3 Maintenance policy
2244 L<perlpolicy> now contains the policy on what patches are acceptable for
2245 maintenance branches (5.12.1).
2247 =head3 Deprecation policy
2249 L<perlpolicy> now contains the policy on compatibility and deprecation
2250 along with definitions of terms like "deprecation" (5.12.2).
2252 =head3 New descriptions in L<perldiag>
2254 The following existing diagnostics are now documented:
2260 L<Ambiguous use of %c resolved as operator %c|perldiag/"Ambiguous use of %c resolved as operator %c">
2264 L<Ambiguous use of %c{%s} resolved to %c%s|perldiag/"Ambiguous use of %c{%s} resolved to %c%s">
2268 L<Ambiguous use of %c{%s%s} resolved to %c%s%s|perldiag/"Ambiguous use of %c{%s%s} resolved to %c%s%s">
2272 L<Ambiguous use of -%s resolved as -&%s()|perldiag/"Ambiguous use of -%s resolved as -&%s()">
2276 L<Invalid strict version format (%s)|perldiag/"Invalid strict version format (%s)">
2280 L<Invalid version format (%s)|perldiag/"Invalid version format (%s)">
2284 L<Invalid version object|perldiag/"Invalid version object">
2290 L<perlbook> has been expanded to cover many more popular books.
2292 =head3 C<SvTRUE> macro
2294 The documentation for the C<SvTRUE> macro in
2295 L<perlapi> was simply wrong in stating that
2296 get-magic is not processed. It has been corrected.
2298 =head3 L<perlvar> revamp
2300 L<perlvar> reorders the variables and groups them by topic. Each variable
2301 introduced after Perl 5.000 notes the first version in which it is
2302 available. L<perlvar> also has a new section for deprecated variables to
2303 note when they were removed.
2305 =head3 Array and hash slices in scalar context
2307 These are now documented in L<perldata>.
2309 =head3 C<use locale> and formats
2311 L<perlform> and L<perllocale> have been corrected to state that
2312 C<use locale> affects formats.
2316 L<overload>'s documentation has practically undergone a rewrite. It
2317 is now much more straightforward and clear.
2319 =head3 perlhack and perlrepository revamp
2321 The L<perlhack> and perlrepository documents have been heavily edited and
2322 split up into several new documents.
2324 The L<perlhack> document is now much shorter, and focuses on the Perl 5
2325 development process and submitting patches
2326 to Perl. The technical content has
2327 been moved to several new documents, L<perlsource>, L<perlinterp>,
2328 L<perlhacktut>, and L<perlhacktips>. This technical content has only been
2331 The perlrepository document has been renamed to
2332 L<perlgit>. This new document is just a how-to
2333 on using git with the Perl source code. Any other content
2334 that used to be in perlrepository has been moved to perlhack.
2336 =head3 Time::Piece examples
2338 Examples in L<perlfaq4> have been updated to show the use of
2343 The following additions or changes have been made to diagnostic output,
2344 including warnings and fatal error messages. For the complete list of
2345 diagnostic messages, see L<perldiag>.
2347 =head2 New Diagnostics
2353 =item Closure prototype called
2355 This error occurs when a subroutine reference passed to an attribute
2356 handler is called, if the subroutine is a closure [perl #68560].
2358 =item Insecure user-defined property %s
2360 Perl detected tainted data when trying to compile a regular
2361 expression that contains a call to a user-defined character property
2362 function, i.e. C<\p{IsFoo}> or C<\p{InFoo}>.
2363 See L<perlunicode/User-Defined Character Properties> and L<perlsec>.
2365 =item panic: gp_free failed to free glob pointer - something is repeatedly re-creating entries
2367 This new error is triggered if a destructor called on an object in a
2368 typeglob that is being freed creates a new typeglob entry containing an
2369 object with a destructor that creates a new entry containing an object....
2371 =item Parsing code internal error (%s)
2373 This new fatal error is produced when parsing
2374 code supplied by an extension violates the
2375 parser's API in a detectable way.
2377 =item refcnt: fd %d%s
2379 This new error only occurs if a internal consistency check fails when a
2380 pipe is about to be closed.
2382 =item Regexp modifier "/%c" may not appear twice
2384 The regular expression pattern has one of the
2385 mutually exclusive modifiers repeated.
2387 =item Regexp modifiers "/%c" and "/%c" are mutually exclusive
2389 The regular expression pattern has more than one of the mutually
2390 exclusive modifiers.
2392 =item Using !~ with %s doesn't make sense
2394 This error occurs when C<!~> is used with C<s///r> or C<y///r>.
2402 =item "\b{" is deprecated; use "\b\{" instead
2404 =item "\B{" is deprecated; use "\B\{" instead
2406 Use of an unescaped "{" immediately following a C<\b> or C<\B> is now
2407 deprecated so as to reserve its use for Perl itself in a future release.
2409 =item Operation "%s" returns its argument for ...
2411 Performing an operation requiring Unicode semantics (such as case-folding)
2412 on a Unicode surrogate or a non-Unicode character now triggers this
2415 =item Use of qw(...) as parentheses is deprecated
2417 See L</"Use of qw(...) as parentheses">, above, for details.
2421 =head2 Changes to Existing Diagnostics
2427 The "Variable $foo is not imported" warning that precedes a
2428 C<strict 'vars'> error has now been assigned the "misc" category, so that
2429 C<no warnings> will suppress it [perl #73712].
2433 C<warn> and C<die> now produce 'Wide character' warnings when fed a
2434 character outside the byte range if STDERR is a byte-sized handle.
2438 The 'Layer does not match this perl' error message has been replaced with
2439 these more helpful messages [perl #73754]:
2445 PerlIO layer function table size (%d) does not match size expected by this
2450 PerlIO layer instance size (%d) does not match size expected by this perl
2457 The "Found = in conditional" warning that is emitted when a constant is
2458 assigned to a variable in a condition is now withheld if the constant is
2459 actually a subroutine or one generated by C<use constant>, since the value
2460 of the constant may not be known at the time the program is written
2465 Previously, if none of the C<gethostbyaddr>, C<gethostbyname> and
2466 C<gethostent> functions were implemented on a given platform, they would
2467 all die with the message 'Unsupported socket function "gethostent" called',
2468 with analogous messages for C<getnet*> and C<getserv*>. This has been
2473 The warning message about unrecognized regular expression escapes passed
2474 through has been changed to include any literal '{' following the
2475 two-character escape. E.g., "\q{" is now emitted instead of "\q".
2479 =head1 Utility Changes
2487 L<perlbug> now looks in the EMAIL environment variable for a return address
2488 if the REPLY-TO and REPLYTO variables are empty.
2492 L<perlbug> did not previously generate a From: header, potentially
2493 resulting in dropped mail. Now it does include that header.
2497 The user's address is now used as the return-path.
2499 Many systems these days don't have a valid Internet domain name and
2500 perlbug@perl.org does not accept email with a return-path that does
2501 not resolve. So the user's address is now passed to sendmail so it's
2502 less likely to get stuck in a mail queue somewhere [perl #82996].
2506 L<perlbug> now always gives the reporter a chance to change the email
2507 address it guesses for them (5.12.2).
2511 L<perlbug> should no longer warn about uninitialized values when using the C<-d>
2512 and C<-v> options (5.12.2).
2516 =head3 L<perl5db.pl>
2522 The remote terminal works after forking and spawns new sessions - one
2523 for each forked process.
2533 L<ptargrep> is a new utility to apply pattern matching to the contents of
2534 files in a tar archive. It comes with C<Archive::Tar>.
2538 =head1 Configuration and Compilation
2540 See also L</"Naming fixes in Policy_sh.SH may invalidate Policy.sh">,
2547 CCINCDIR and CCLIBDIR for the mingw64
2548 cross-compiler are now correctly under
2549 $(CCHOME)\mingw\include and \lib rather than immediately below $(CCHOME).
2551 This means the 'incpath', 'libpth', 'ldflags', 'lddlflags' and
2552 'ldflags_nolargefiles' values in Config.pm and Config_heavy.pl are now
2557 'make test.valgrind' has been adjusted to account for cpan/dist/ext
2562 On compilers that support it, C<-Wwrite-strings> is now added to cflags by
2567 The C<Encode> module can now (once again) be included in a static Perl
2568 build. The special-case handling for this situation got broken in Perl
2569 5.11.0, and has now been repaired.
2573 The previous default size of a PerlIO buffer (4096 bytes) has been increased
2574 to the larger of 8192 bytes and your local BUFSIZ. Benchmarks show that doubling
2575 this decade-old default increases read and write performance in the neighborhood
2576 of 25% to 50% when using the default layers of perlio on top of unix. To choose
2577 a non-default size, such as to get back the old value or to obtain an even
2578 larger value, configure with:
2580 ./Configure -Accflags=-DPERLIOBUF_DEFAULT_BUFSIZ=N
2582 where N is the desired size in bytes; it should probably be a multiple of
2587 An "incompatible operand types" error in ternary expressions when building
2588 with C<clang> has been fixed (5.12.2).
2592 Perl now skips setuid C<File::Copy> tests on partitions it detects to be mounted
2593 as C<nosuid> (5.12.2).
2597 =head1 Platform Support
2599 =head2 New Platforms
2605 Perl now builds on AIX 4.2 (5.12.1).
2609 =head2 Discontinued Platforms
2613 =item Apollo DomainOS
2615 The last vestiges of support for this platform have been excised from the
2616 Perl distribution. It was officially discontinued
2617 in version 5.12.0. It had
2618 not worked for years before that.
2622 The last vestiges of support for this platform have been excised from the
2623 Perl distribution. It was officially discontinued in an earlier version.
2627 =head2 Platform-Specific Notes
2635 F<README.aix> has been updated with information about the XL C/C++ V11 compiler
2646 The C<d_u32align> configuration probe on ARM has been fixed (5.12.2).
2656 MakeMaker has been updated to build man pages on cygwin.
2660 Improved rebase behaviour
2662 If a dll is updated on cygwin the old imagebase address is reused.
2663 This solves most rebase errors, especially when updating on core dll's.
2664 See L<http://www.tishler.net/jason/software/rebase/rebase-2.4.2.README> for more information.
2668 Support for the standard cygwin dll prefix, which is e.g. needed for FFI's
2672 Updated build hints file
2682 FreeBSD 7 no longer contains F</usr/bin/objformat>. At build time,
2683 Perl now skips the F<objformat> check for versions 7 and higher and
2684 assumes ELF (5.12.1).
2694 Perl now allows -Duse64bitint without promoting to use64bitall on HP-UX
2705 Conversion of strings to floating-point numbers is now more accurate on
2706 IRIX systems [perl #32380].
2716 Early versions of Mac OS X (Darwin) had buggy implementations of the
2717 C<setregid>, C<setreuid>, C<setrgid> and C<setruid> functions, so perl
2718 would pretend they did not exist.
2720 These functions are now recognised on Mac OS 10.5 (Leopard; Darwin 9) and
2721 higher, as they have been fixed [perl #72990].
2731 Previously if you built perl with a shared libperl.so on MirBSD (the
2732 default config), it would work up to the installation; however, once
2733 installed, it would be unable to find libperl. So path handling is now
2734 treated as in the other BSD dialects.
2744 The NetBSD hints file has been changed to make the system's malloc the
2749 =head3 Recent OpenBSDs now use perl's malloc
2755 OpenBSD E<gt> 3.7 has a new malloc implementation which is mmap-based
2756 and as such can release memory back to the OS; however, perl's use of
2757 this malloc causes a substantial slowdown so we now default to using
2758 perl's malloc instead [perl #75742].
2768 perl now builds again with OpenVOS (formerly known as Stratus VOS)
2769 [perl #78132] (5.12.3).
2779 DTrace is now supported on Solaris. There used to be build failures, but
2780 these have been fixed [perl #73630] (5.12.3).
2790 It's now possible to build extensions on older (pre 7.3-2) VMS systems.
2792 DCL symbol length was limited to 1K up until about seven years or
2793 so ago, but there was no particularly deep reason to prevent those
2794 older systems from configuring and building Perl (5.12.1).
2798 We fixed the previously-broken C<-Uuseperlio> build on VMS.
2800 We were checking a variable that doesn't exist in the non-default
2801 case of disabling perlio. Now we only look at it when it exists (5.12.1).
2805 We fixed the -Uuseperlio command-line option in configure.com.
2807 Formerly it only worked if you went through all the questions
2808 interactively and explicitly answered no (5.12.1).
2812 C<PerlIOUnix_open> now honours the default permissions on VMS.
2814 When C<perlio> became the default and C<unixio> became the default bottom layer,
2815 the most common path for creating files from Perl became C<PerlIOUnix_open>,
2816 which has always explicitly used C<0666> as the permission mask.
2818 To avoid this, C<0777> is now passed as the permissions to C<open()>. In the
2819 VMS CRTL, C<0777> has a special meaning over and above intersecting with the
2820 current umask; specifically, it allows Unix syscalls to preserve native default
2821 permissions (5.12.3).
2825 Spurious record boundaries are no longer
2826 introduced by the PerlIO layer during output (5.12.3).
2830 The shortening of symbols longer than 31 characters in the C sources is
2831 now done by the compiler rather than by xsubpp (which could only do so
2832 for generated symbols in XS code).
2836 Record-oriented files (record format variable or variable with fixed control)
2837 opened for write by the perlio layer will now be line-buffered to prevent the
2838 introduction of spurious line breaks whenever the perlio buffer fills up.
2842 F<git_version.h> is now installed on VMS. This
2843 was an oversight in v5.12.0 which
2844 caused some extensions to fail to build (5.12.2).
2848 Several memory leaks in L<stat()|perlfunc/"stat FILEHANDLE"> have been fixed (5.12.2).
2852 A memory leak in C<Perl_rename()> due to a double allocation has been
2857 A memory leak in C<vms_fid_to_name()> (used by C<realpath()> and
2858 C<realname()>) has been fixed (5.12.2).
2864 See also L</"fork() emulation will not wait for signalled children"> and
2865 L</"Perl source code is read in text mode on Windows">, above.
2871 Fixed build process for SDK2003SP1 compilers.
2875 Compilation with Visual Studio 2010 is now supported.
2879 When using old 32-bit compilers, the define C<_USE_32BIT_TIME_T> will now
2880 be set in C<$Config{ccflags}>. This improves portability when compiling
2881 XS extensions using new compilers, but for a perl compiled with old 32-bit
2886 C<$Config{gccversion}> is now set correctly when perl is built using the
2887 mingw64 compiler from L<http://mingw64.org> [perl #73754].
2891 When building Perl with the mingw64 x64 cross-compiler C<incpath>,
2892 C<libpth>, C<ldflags>, C<lddlflags> and C<ldflags_nolargefiles> values
2893 in F<Config.pm> and F<Config_heavy.pl> were not previously being set
2894 correctly because, with that compiler, the include and lib directories
2895 are not immediately below C<$(CCHOME)> (5.12.2).
2899 The build process proceeds more smoothly with mingw and dmake when
2900 F<C:\MSYS\bin> is in the PATH, due to a C<Cwd> fix.
2904 Support for building with Visual C++ 2010 is now underway, but is not yet
2905 complete. See F<README.win32> or L<perlwin32> for more details.
2909 The option to use an externally-supplied C<crypt()>, or to build with no
2910 C<crypt()> at all, has been removed. Perl supplies its own C<crypt()>
2911 implementation for Windows, and the political situation that required
2912 this part of the distribution to sometimes be omitted is long gone.
2916 =head1 Internal Changes
2920 =head3 CLONE_PARAMS structure added to ease correct thread creation
2922 Modules that create threads should now create C<CLONE_PARAMS> structures
2923 by calling the new function C<Perl_clone_params_new()>, and free them with
2924 C<Perl_clone_params_del()>. This will ensure compatibility with any future
2925 changes to the internals of the C<CLONE_PARAMS> structure layout, and that
2926 it is correctly allocated and initialised.
2928 =head3 New parsing functions
2930 Several functions have been added for parsing statements or multiple
2937 C<parse_fullstmt> parses a complete Perl statement.
2941 C<parse_stmtseq> parses a sequence of statements, up
2942 to closing brace or EOF.
2946 C<parse_block> parses a block [perl #78222].
2950 C<parse_barestmt> parses a statement
2955 C<parse_label> parses a statement label, separate from statements.
2960 L<C<parse_fullexpr()>|perlapi/parse_fullexpr>,
2961 L<C<parse_listexpr()>|perlapi/parse_listexpr>,
2962 L<C<parse_termexpr()>|perlapi/parse_termexpr>, and
2963 L<C<parse_arithexpr()>|perlapi/parse_arithexpr>
2964 functions have been added to the API. They perform
2965 recursive-descent parsing of expressions at various precedence levels.
2966 They are expected to be used by syntax plugins.
2968 See L<perlapi> for details.
2970 =head3 Hints hash API
2972 A new C API for introspecting the hinthash C<%^H> at runtime has been
2973 added. See C<cop_hints_2hv>, C<cop_hints_fetchpvn>, C<cop_hints_fetchpvs>,
2974 C<cop_hints_fetchsv>, and C<hv_copy_hints_hv> in L<perlapi> for details.
2976 A new, experimental API has been added for accessing the internal
2977 structure that Perl uses for C<%^H>. See the functions beginning with
2978 C<cophh_> in L<perlapi>.
2980 =head3 C interface to C<caller()>
2982 The C<caller_cx> function has been added as an XSUB-writer's equivalent of
2983 C<caller()>. See L<perlapi> for details.
2985 =head3 Custom per-subroutine check hooks
2987 XS code in an extension module can now annotate a subroutine (whether
2988 implemented in XS or in Perl) so that nominated XS code will be called
2989 at compile time (specifically as part of op checking) to change the op
2990 tree of that subroutine. The compile-time check function (supplied by
2991 the extension module) can implement argument processing that can't be
2992 expressed as a prototype, generate customised compile-time warnings,
2993 perform constant folding for a pure function, inline a subroutine
2994 consisting of sufficiently simple ops, replace the whole call with a
2995 custom op, and so on. This was previously all possible by hooking the
2996 C<entersub> op checker, but the new mechanism makes it easy to tie the
2997 hook to a specific subroutine. See L<perlapi/cv_set_call_checker>.
2999 To help in writing custom check hooks, several subtasks within standard
3000 C<entersub> op checking have been separated out and exposed in the API.
3002 =head3 Improved support for custom OPs
3004 Custom ops can now be registered with the new C<custom_op_register> C
3005 function and the C<XOP> structure. This will make it easier to add new
3006 properties of custom ops in the future. Two new properties have been added
3007 already, C<xop_class> and C<xop_peep>.
3009 C<xop_class> is one of the OA_*OP constants, and allows L<B> and other
3010 introspection mechanisms to work with custom ops
3011 that aren't BASEOPs. C<xop_peep> is a pointer to
3012 a function that will be called for ops of this
3013 type from C<Perl_rpeep>.
3015 See L<perlguts/Custom Operators> and L<perlapi/Custom Operators> for more
3018 The old C<PL_custom_op_names>/C<PL_custom_op_descs> interface is still
3019 supported but discouraged.
3023 It is now possible for XS code to hook into Perl's lexical scope
3024 mechanism at compile time, using the new C<Perl_blockhook_register>
3025 function. See L<perlguts/"Compile-time scope hooks">.
3027 =head3 The recursive part of the peephole optimizer is now hookable
3029 In addition to C<PL_peepp>, for hooking into the toplevel peephole optimizer, a
3030 C<PL_rpeepp> is now available to hook into the optimizer recursing into
3031 side-chains of the optree.
3033 =head3 New non-magical variants of existing functions
3035 The following functions/macros have been added to the API. The C<*_nomg>
3036 macros are equivalent to their non-_nomg variants, except that they ignore
3037 get-magic. Those ending in C<_flags> allow one to specify whether
3038 get-magic is processed.
3049 In some of these cases, the non-_flags functions have
3050 been replaced with wrappers around the new functions.
3052 =head3 pv/pvs/sv versions of existing functions
3054 Many functions ending with pvn now have equivalent pv/pvs/sv versions.
3056 =head3 List op-building functions
3058 List op-building functions have been added to the
3059 API. See L<op_append_elem|perlapi/op_append_elem>,
3060 L<op_append_list|perlapi/op_append_list>, and
3061 L<op_prepend_elem|perlapi/op_prepend_elem> in L<perlapi>.
3065 The L<LINKLIST|perlapi/LINKLIST> macro, part of op building that
3066 constructs the execution-order op chain, has been added to the API.
3068 =head3 Localisation functions
3070 The C<save_freeop>, C<save_op>, C<save_pushi32ptr> and C<save_pushptrptr>
3071 functions have been added to the API.
3075 A stash can now have a list of effective names in addition to its usual
3076 name. The first effective name can be accessed via the C<HvENAME> macro,
3077 which is now the recommended name to use in MRO linearisations (C<HvNAME>
3078 being a fallback if there is no C<HvENAME>).
3080 These names are added and deleted via C<hv_ename_add> and
3081 C<hv_ename_delete>. These two functions are I<not> part of the API.
3083 =head3 New functions for finding and removing magic
3085 The L<C<mg_findext()>|perlapi/mg_findext> and
3086 L<C<sv_unmagicext()>|perlapi/sv_unmagicext>
3087 functions have been added to the API.
3088 They allow extension authors to find and remove magic attached to
3089 scalars based on both the magic type and the magic virtual table, similar to how
3090 C<sv_magicext()> attaches magic of a certain type and with a given virtual table
3091 to a scalar. This eliminates the need for extensions to walk the list of
3092 C<MAGIC> pointers of an C<SV> to find the magic that belongs to them.
3094 =head3 C<find_rundefsv>
3096 This function returns the SV representing C<$_>, whether it's lexical
3099 =head3 C<Perl_croak_no_modify>
3101 C<Perl_croak_no_modify()> is short-hand for
3102 C<Perl_croak("%s", PL_no_modify)>.
3104 =head3 C<PERL_STATIC_INLINE> define
3106 The C<PERL_STATIC_INLINE> define has been added to provide the best-guess
3107 incantation to use for static inline functions, if the C compiler supports
3108 C99-style static inline. If it doesn't, it'll give a plain C<static>.
3110 C<HAS_STATIC_INLINE> can be used to check if the compiler actually supports
3113 =head3 New C<pv_escape> option for hexadecimal escapes
3115 A new option, C<PERL_PV_ESCAPE_NONASCII>, has been added to C<pv_escape> to
3116 dump all characters above ASCII in hexadecimal. Before, one could get all
3117 characters as hexadecimal or the Latin1 non-ASCII as octal.
3121 C<lex_start> has been added to the API, but is considered experimental.
3123 =head3 C<op_scope()> and C<op_lvalue()>
3125 The C<op_scope()> and C<op_lvalue()> functions have been added to the API,
3126 but are considered experimental.
3128 =head2 C API Changes
3130 =head3 C<PERL_POLLUTE> has been removed
3132 The option to define C<PERL_POLLUTE> to expose older 5.005 symbols for
3133 backwards compatibility has been removed. It's use was always discouraged,
3134 and MakeMaker contains a more specific escape hatch:
3136 perl Makefile.PL POLLUTE=1
3138 This can be used for modules that have not been upgraded to 5.6 naming
3139 conventions (and really should be completely obsolete by now).
3141 =head3 Check API compatibility when loading XS modules
3143 When perl's API changes in incompatible ways (which usually happens between
3144 major releases), XS modules compiled for previous versions of perl will not
3145 work anymore. They will need to be recompiled against the new perl.
3147 In order to ensure that modules are recompiled, and to prevent users from
3148 accidentally loading modules compiled for old perls into newer ones, the
3149 C<XS_APIVERSION_BOOTCHECK> macro has been added. That macro, which is
3150 called when loading every newly compiled extension, compares the API
3151 version of the running perl with the version a module has been compiled for
3152 and raises an exception if they don't match.
3154 =head3 Perl_fetch_cop_label
3156 The first argument of the C API function C<Perl_fetch_cop_label> has changed
3157 from C<struct refcounted he *> to C<COP *>, to insulate the user from
3158 implementation details.
3160 This API function was marked as "may change", and likely isn't in use outside
3161 the core. (Neither an unpacked CPAN, nor Google's codesearch, finds any other
3164 =head3 GvCV() and GvGP() are no longer lvalues
3166 The new GvCV_set() and GvGP_set() macros are now provided to replace
3167 assignment to those two macros.
3169 This allows a future commit to eliminate some backref magic between GV
3170 and CVs, which will require complete control over assignment to the
3173 =head3 CvGV() is no longer an lvalue
3175 Under some circumstances, the C<CvGV()> field of a CV is now
3176 reference-counted. To ensure consistent behaviour, direct assignment to
3177 it, for example C<CvGV(cv) = gv> is now a compile-time error. A new macro,
3178 C<CvGV_set(cv,gv)> has been introduced to perform this operation
3179 safely. Note that modification of this field is not part of the public
3180 API, regardless of this new macro (and despite its being listed in this section).
3182 =head3 CvSTASH() is no longer an lvalue
3184 The C<CvSTASH()> macro can now only be used as an rvalue. C<CvSTASH_set()>
3185 has been added to replace assignment to C<CvSTASH()>. This is to ensure
3186 that backreferences are handled properly. These macros are not part of the
3189 =head3 Calling conventions for C<newFOROP> and C<newWHILEOP>
3191 The way the parser handles labels has been cleaned up and refactored. As a
3192 result, the C<newFOROP()> constructor function no longer takes a parameter
3193 stating what label is to go in the state op.
3195 The C<newWHILEOP()> and C<newFOROP()> functions no longer accept a line
3196 number as a parameter.
3198 =head3 Flags passed to C<uvuni_to_utf8_flags> and C<utf8n_to_uvuni>
3200 Some of the flags parameters to uvuni_to_utf8_flags() and
3201 utf8n_to_uvuni() have changed. This is a result of Perl's now allowing
3202 internal storage and manipulation of code points that are problematic
3203 in some situations. Hence, the default actions for these functions has
3204 been complemented to allow these code points. The new flags are
3205 documented in L<perlapi>. Code that requires the problematic code
3206 points to be rejected needs to change to use the new flags. Some flag
3207 names are retained for backward source compatibility, though they do
3208 nothing, as they are now the default. However the flags
3209 C<UNICODE_ALLOW_FDD0>, C<UNICODE_ALLOW_FFFF>, C<UNICODE_ILLEGAL>, and
3210 C<UNICODE_IS_ILLEGAL> have been removed, as they stem from a
3211 fundamentally broken model of how the Unicode non-character code points
3212 should be handled, which is now described in
3213 L<perlunicode/Non-character code points>. See also the Unicode section
3214 under L</Selected Bug Fixes>.
3216 =head2 Deprecated C APIs
3220 =item C<Perl_ptr_table_clear>
3222 C<Perl_ptr_table_clear> is no longer part of Perl's public API. Calling it
3223 now generates a deprecation warning, and it will be removed in a future
3226 =item C<sv_compile_2op>
3228 The C<sv_compile_2op()> API function is now deprecated. Searches suggest
3229 that nothing on CPAN is using it, so this should have zero impact.
3231 It attempted to provide an API to compile code down to an optree, but failed
3232 to bind correctly to lexicals in the enclosing scope. It's not possible to
3233 fix this problem within the constraints of its parameters and return value.
3235 =item C<find_rundefsvoffset>
3237 The C<find_rundefsvoffset> function has been deprecated. It appeared that
3238 its design was insufficient for reliably getting the lexical C<$_> at
3241 Use the new C<find_rundefsv> function or the C<UNDERBAR> macro
3242 instead. They directly return the right SV
3243 representing C<$_>, whether it's
3246 =item C<CALL_FPTR> and C<CPERLscope>
3248 Those are left from an old implementation of C<MULTIPLICITY> using C++ objects,
3249 which was removed in Perl 5.8. Nowadays these macros do exactly nothing, so
3250 they shouldn't be used anymore.
3252 For compatibility, they are still defined for external C<XS> code. Only
3253 extensions defining C<PERL_CORE> must be updated now.
3257 =head2 Other Internal Changes
3259 =head3 Stack unwinding
3261 The protocol for unwinding the C stack at the last stage of a C<die>
3262 has changed how it identifies the target stack frame. This now uses
3263 a separate variable C<PL_restartjmpenv>, where previously it relied on
3264 the C<blk_eval.cur_top_env> pointer in the C<eval> context frame that
3265 has nominally just been discarded. This change means that code running
3266 during various stages of Perl-level unwinding no longer needs to take
3267 care to avoid destroying the ghost frame.
3269 =head3 Scope stack entries
3271 The format of entries on the scope stack has been changed, resulting in a
3272 reduction of memory usage of about 10%. In particular, the memory used by
3273 the scope stack to record each active lexical variable has been halved.
3275 =head3 Memory allocation for pointer tables
3277 Memory allocation for pointer tables has been changed. Previously
3278 C<Perl_ptr_table_store> allocated memory from the same arena system as
3279 C<SV> bodies and C<HE>s, with freed memory remaining bound to those arenas
3280 until interpreter exit. Now it allocates memory from arenas private to the
3281 specific pointer table, and that memory is returned to the system when
3282 C<Perl_ptr_table_free> is called. Additionally, allocation and release are
3283 both less CPU intensive.
3287 The C<UNDERBAR> macro now calls C<find_rundefsv>. C<dUNDERBAR> is now a
3288 noop but should still be used to ensure past and future compatibility.
3290 =head3 String comparison routines renamed
3292 The ibcmp_* functions have been renamed and are now called foldEQ,
3293 foldEQ_locale and foldEQ_utf8. The old names are still available as
3296 =head3 C<chop> and C<chomp> implementations merged
3298 The opcode bodies for C<chop> and C<chomp> and for C<schop> and C<schomp>
3299 have been merged. The implementation functions C<Perl_do_chop()> and
3300 C<Perl_do_chomp()>, never part of the public API, have been merged and
3301 moved to a static function in F<pp.c>. This shrinks the perl binary
3302 slightly, and should not affect any code outside the core (unless it is
3303 relying on the order of side effects when C<chomp> is passed a I<list> of
3306 =head1 Selected Bug Fixes
3314 Perl no longer produces this warning:
3316 $ perl -we 'open my $f, ">", \my $x; binmode $f, "scalar"'
3317 Use of uninitialized value in binmode at -e line 1.
3321 Opening a glob reference via C<< open $fh, "E<gt>", \*glob >> will no longer
3322 cause the glob to be corrupted when the filehandle is printed to. This would
3323 cause perl to crash whenever the glob's contents were accessed
3328 PerlIO no longer crashes when called recursively, e.g., from a signal
3329 handler. Now it just leaks memory [perl #75556].
3333 Most I/O functions were not warning for unopened handles unless the
3334 'closed' and 'unopened' warnings categories were both enabled. Now only
3335 C<use warnings 'unopened'> is necessary to trigger these warnings (as was
3336 always meant to be the case).
3340 There have been several fixes to PerlIO layers:
3342 When C<binmode FH, ":crlf"> pushes the C<:crlf> layer on top of the stack,
3343 it no longer enables crlf layers lower in the stack, to avoid unexpected
3344 results [perl #38456].
3346 Opening a file in C<:raw> mode now does what it advertises to do (first
3347 open the file, then binmode it), instead of simply leaving off the top
3348 layer [perl #80764].
3350 The three layers C<:pop>, C<:utf8> and C<:bytes> didn't allow stacking when
3351 opening a file. For example
3354 open FH, '>:pop:perlio', 'some.file' or die $!;
3356 Would throw an error: "Invalid argument". This has been fixed in this
3357 release [perl #82484].
3361 =head2 Regular Expression Bug Fixes
3367 The regular expression engine no longer loops when matching
3368 C<"\N{LATIN SMALL LIGATURE FF}" =~ /f+/i> and similar expressions
3369 [perl #72998] (5.12.1).
3373 The trie runtime code should no longer allocate massive amounts of memory,
3378 Syntax errors in C<< (?{...}) >> blocks no longer cause panic messages
3383 A pattern like C<(?:(o){2})?> no longer causes a "panic" error
3388 A fatal error in regular expressions containing C<(.*?)> when processing
3389 UTF-8 data has been fixed [perl #75680] (5.12.2).
3393 An erroneous regular expression engine optimisation that caused regex verbs like
3394 C<*COMMIT> sometimes to be ignored has been removed.
3398 The regular expression bracketed character class C<[\8\9]> was effectively the
3399 same as C<[89\000]>, incorrectly matching a NULL character. It also gave
3400 incorrect warnings that the C<8> and C<9> were ignored. Now C<[\8\9]> is the
3401 same as C<[89]> and gives legitimate warnings that C<\8> and C<\9> are
3402 unrecognized escape sequences, passed-through.
3406 A regular expression match in the right-hand side of a global substitution
3407 (C<s///g>) that is in the same scope will no longer cause match variables
3408 to have the wrong values on subsequent iterations. This can happen when an
3409 array or hash subscript is interpolated in the right-hand side, as in
3410 C<s|(.)|@a{ print($1), /./ }|g> [perl #19078].
3414 Several cases in which characters in the Latin-1 non-ASCII range (0x80 to
3415 0xFF) used not to match themselves or used to match both a character class
3416 and its complement have been fixed. For instance, U+00E2 could match both
3417 C<\w> and C<\W> [perl #78464] [perl #18281] [perl #60156].
3421 Matching a Unicode character against an alternation containing characters
3422 that happened to match continuation bytes in the former's UTF8
3423 representation (C<qq{\x{30ab}} =~ /\xab|\xa9/>) would cause erroneous
3424 warnings [perl #70998].
3428 The trie optimisation was not taking empty groups into account, preventing
3429 'foo' from matching C</\A(?:(?:)foo|bar|zot)\z/> [perl #78356].
3433 A pattern containing a C<+> inside a lookahead would sometimes cause an
3434 incorrect match failure in a global match (e.g., C</(?=(\S+))/g>)
3439 A regular expression optimisation would sometimes cause a match with a
3440 C<{n,m}> quantifier to fail when it should match [perl #79152].
3444 Case insensitive matching in regular expressions compiled under C<use
3445 locale> now works much more sanely when the pattern or
3446 target string is encoded internally in
3447 UTF8. Previously, under these conditions the localeness
3448 was completely lost. Now, code points above 255 are treated as Unicode,
3449 but code points between 0 and 255 are treated using the current locale
3450 rules, regardless of whether the pattern or the string is encoded in UTF8.
3451 The few case-insensitive matches that cross the 255/256 boundary are not
3452 allowed. For example, 0xFF does not caselessly match the character at
3453 0x178, LATIN CAPITAL LETTER Y WITH DIAERESIS, because 0xFF may not be
3454 LATIN SMALL LETTER Y in the current locale, and Perl has no way of
3455 knowing if that character even exists in the locale, much less what code
3460 The C<(?|...)> regular expression construct no longer crashes if the final
3461 branch has more sets of capturing parentheses than any other branch. This
3462 was fixed in Perl 5.10.1 for the case of a single branch, but that fix did
3463 not take multiple branches into account [perl #84746].
3467 A bug has been fixed in the implementation of C<{...}> quantifiers in
3468 regular expressions that prevented the code block in
3469 C</((\w+)(?{ print $2 })){2}/> from seeing the C<$2> sometimes
3474 =head2 Syntax/Parsing Bugs
3480 C<when(scalar){...}> no longer crashes, but produces a syntax error
3481 [perl #74114] (5.12.1).
3485 A label right before a string eval (C<foo: eval $string>) no longer causes
3486 the label to be associated also with the first statement inside the eval
3487 [perl #74290] (5.12.1).
3491 The C<no 5.13.2;> form of C<no> no longer tries to turn on features or
3492 pragmata (i.e., strict) [perl #70075] (5.12.2).
3496 C<BEGIN {require 5.12.0}> now behaves as documented, rather than behaving
3497 identically to C<use 5.12.0;>. Previously, C<require> in a C<BEGIN> block
3498 was erroneously executing the C<use feature ':5.12.0'> and
3499 C<use strict;> behaviour, which only C<use> was documented to
3500 provide [perl #69050].
3504 A regression introduced in Perl 5.12.0, making
3505 C<< my $x = 3; $x = length(undef) >> result in C<$x> set to C<3> has been
3506 fixed. C<$x> will now be C<undef> [perl #85508] (5.12.2).
3510 When strict 'refs' mode is off, C<%{...}> in rvalue context returns
3511 C<undef> if its argument is undefined. An optimisation introduced in perl
3512 5.12.0 to make C<keys %{...}> faster when used as a boolean did not take
3513 this into account, causing C<keys %{+undef}> (and C<keys %$foo> when
3514 C<$foo> is undefined) to be an error, which it should only be in strict
3519 Constant-folding used to cause
3521 $text =~ ( 1 ? /phoo/ : /bear/)
3527 at compile time. Now it correctly matches against C<$_> [perl #20444].
3531 Parsing Perl code (either with string C<eval> or by loading modules) from
3532 within a C<UNITCHECK> block no longer causes the interpreter to crash
3537 String evals no longer fail after 2 billion scopes have been
3538 compiled [perl #83364].
3542 The parser no longer hangs when encountering certain Unicode characters,
3543 such as U+387 [perl #74022].
3547 Several contexts no longer allow a Unicode character to begin a word
3548 that should never begin words, for an example an accent that must follow
3549 another character previously could precede all other characters.
3553 Defining a constant with the same name as one of perl's special blocks
3554 (e.g., INIT) stopped working in 5.12.0, but has now been fixed
3559 A reference to a literal value used as a hash key (C<$hash{\"foo"}>) used
3560 to be stringified, even if the hash was tied [perl #79178].
3564 A closure containing an C<if> statement followed by a constant or variable
3565 is no longer treated as a constant [perl #63540].
3569 C<state> can now be used with attributes. It
3570 used to mean the same thing as
3571 C<my> if attributes were present [perl #68658].
3575 Expressions like C<< @$a > 3 >> no longer cause C<$a> to be mentioned in
3576 the "Use of uninitialized value in numeric gt" warning when C<$a> is
3577 undefined (since it is not part of the C<E<gt>> expression, but the operand
3578 of the C<@>) [perl #72090].
3582 Accessing an element of a package array with a hard-coded number (as
3583 opposed to an arbitrary expression) would crash if the array did not exist.
3584 Usually the array would be autovivified during compilation, but typeglob
3585 manipulation could remove it, as in these two cases which used to crash:
3587 *d = *a; print $d[0];
3588 undef *d; print $d[0];
3592 The C<-C> command line option, when used on the shebang line, can now be
3593 followed by other options [perl #72434].
3597 The C<B> module was returning C<B::OP>s instead of C<B::LOGOP>s for C<entertry> [perl #80622].
3598 This was due to a bug in the perl core, not in C<B> itself.
3602 =head2 Stashes, Globs and Method Lookup
3604 Perl 5.10.0 introduced a new internal mechanism for caching MROs (method
3605 resolution orders, or lists of parent classes; aka "isa" caches) to make
3606 method lookup faster (so @ISA arrays would not have to be searched
3607 repeatedly). Unfortunately, this brought with it quite a few bugs. Almost
3608 all of these have been fixed now, along with a few MRO-related bugs that
3609 existed before 5.10.0:
3615 The following used to have erratic effects on method resolution, because
3616 the "isa" caches were not reset or otherwise ended up listing the wrong
3617 classes. These have been fixed.
3621 =item Aliasing packages by assigning to globs [perl #77358]
3623 =item Deleting packages by deleting their containing stash elements
3625 =item Undefining the glob containing a package (C<undef *Foo::>)
3627 =item Undefining an ISA glob (C<undef *Foo::ISA>)
3629 =item Deleting an ISA stash element (C<delete $Foo::{ISA}>)
3631 =item Sharing @ISA arrays between classes (via C<*Foo::ISA = \@Bar::ISA> or
3632 C<*Foo::ISA = *Bar::ISA>) [perl #77238]
3636 C<undef *Foo::ISA> would even stop a new C<@Foo::ISA> array from updating
3641 Typeglob assignments would crash if the glob's stash no longer existed, so
3642 long as the glob assigned to was named 'ISA' or the glob on either side of
3643 the assignment contained a subroutine.
3647 C<PL_isarev>, which is accessible to Perl via C<mro::get_isarev> is now
3648 updated properly when packages are deleted or removed from the C<@ISA> of
3649 other classes. This allows many packages to be created and deleted without
3650 causing a memory leak [perl #75176].
3654 In addition, various other bugs related to typeglobs and stashes have been
3661 Some work has been done on the internal pointers that link between symbol
3662 tables (stashes), typeglobs and subroutines. This has the effect that
3663 various edge cases related to deleting stashes or stash entries (e.g.
3664 <%FOO:: = ()>), and complex typeglob or code reference aliasing, will no
3665 longer crash the interpreter.
3669 Assigning a reference to a glob copy now assigns to a glob slot instead of
3670 overwriting the glob with a scalar [perl #1804] [perl #77508].
3674 A bug when replacing the glob of a loop variable within the loop has been fixed
3676 means the following code will no longer crash:
3684 Assigning a glob to a PVLV used to convert it to a plain string. Now it
3685 works correctly, and a PVLV can hold a glob. This would happen when a
3686 nonexistent hash or array element was passed to a subroutine:
3688 sub { $_[0] = *foo }->($hash{key});
3689 # $_[0] would have been the string "*main::foo"
3691 It also happened when a glob was assigned to, or returned from, an element
3692 of a tied array or hash [perl #36051].
3696 When trying to report C<Use of uninitialized value $Foo::BAR>, crashes could
3697 occur if the glob holding the global variable in question had been detached
3698 from its original stash by, for example, C<delete $::{'Foo::'}>. This has
3699 been fixed by disabling the reporting of variable names in those
3704 During the restoration of a localised typeglob on scope exit, any
3705 destructors called as a result would be able to see the typeglob in an
3706 inconsistent state, containing freed entries, which could result in a
3707 crash. This would affect code like this:
3710 eval { die bless [] }; # puts an object in $@
3715 Now the glob entries are cleared before any destructors are called. This
3716 also means that destructors can vivify entries in the glob. So perl tries
3717 again and, if the entries are re-created too many times, dies with a
3718 'panic: gp_free...' error message.
3722 If a typeglob is freed while a subroutine attached to it is still
3723 referenced elsewhere, the subroutine is renamed to __ANON__ in the same
3724 package, unless the package has been undefined, in which case the __ANON__
3725 package is used. This could cause packages to be autovivified in some
3726 cases; e.g., if the package had been deleted. Now this is no longer the
3727 case. The __ANON__ package is now used also when the original package is
3728 no longer attached to the symbol table. This avoids memory leaks in some
3729 cases [perl #87664].
3739 What has become known as the "Unicode Bug" is almost completely resolved in
3740 this release. Under C<use feature 'unicode_strings'> (which is
3741 automatically selected by C<use 5.012> and above), the internal
3742 storage format of a string no longer affects the external semantics.
3745 There are two known exceptions:
3751 The now-deprecated user-defined case changing
3752 functions require utf8-encoded strings to function. The CPAN module
3753 L<Unicode::Casing> has been written to replace this feature, without its
3754 drawbacks, and the feature is scheduled to be removed in 5.16.
3758 C<quotemeta> (and its in-line equivalent C<\Q>) also can give different
3759 results if a string is encoded in UTF-8 or not. See
3760 L<perlunicode/The "Unicode Bug">.
3766 The handling of Unicode non-character code points has changed.
3767 Previously they were mostly considered illegal, except that only one of
3768 the 66 of them was known about in places. The Unicode standard
3769 considers them legal, but forbids the "open interchange" of them.
3770 This is part of the change to allow the internal use of any code point
3771 (see L</Core Enhancements>). Together, these changes resolve
3772 [perl #38722], [perl #51918], [perl #51936], [perl #63446].
3776 Case-insensitive C<"/i"> regular expression matching of Unicode
3777 characters which match multiple characters now works much more as
3778 intended. For example
3780 "\N{LATIN SMALL LIGATURE FFI}" =~ /ffi/ui
3784 "ffi" =~ /\N{LATIN SMALL LIGATURE FFI}/ui
3786 are both true. Previously, there were many bugs with this feature.
3787 What hasn't been fixed are the places where the pattern contains the
3788 multiple characters, but the characters are split up by other things,
3791 "\N{LATIN SMALL LIGATURE FFI}" =~ /(f)(f)i/ui
3795 "\N{LATIN SMALL LIGATURE FFI}" =~ /ffi*/ui
3799 "\N{LATIN SMALL LIGATURE FFI}" =~ /[a-f][f-m][g-z]/ui
3801 None of these match.
3803 Also, this matching doesn't fully conform to the current Unicode
3804 standard, which asks that the matching be made upon the NFD
3805 (Normalization Form .ecomposed) of the text. However, as of this
3806 writing, March 2010, the Unicode standard is currently in flux about
3807 what they will recommend doing with regard to such cases. It may be
3808 that they will throw out the whole concept of multi-character matches.
3813 Naming a deprecated character in \N{...} no longer leaks memory.
3817 We fixed a bug that could cause \N{} constructs followed by a single . to
3818 be parsed incorrectly [perl #74978] (5.12.1).
3822 C<chop> now correctly handles characters above "\x{7fffffff}"
3827 Passing to C<index> an offset beyond the end of the string when the string
3828 is encoded internally in UTF8 no longer causes panics [perl #75898].
3832 C<warn()> and C<die()> now respect utf8-encoded scalars [perl #45549].
3836 Sometimes the UTF8 length cache would not be reset on a value
3837 returned by substr, causing C<length(substr($uni_string,...))> to give
3838 wrong answers. With C<${^UTF8CACHE}> set to -1, it would produce a 'panic'
3839 error message, too [perl #77692].
3843 =head2 Ties, Overloading and Other Magic
3849 Overloading now works properly in conjunction with tied
3850 variables. What formerly happened was that most ops checked their
3851 arguments for overloading I<before> checking for magic, so for example
3852 an overloaded object returned by a tied array access would usually be
3853 treated as not overloaded [RT #57012].
3857 Various cases of magic (e.g., tie methods) being called on tied variables
3858 too many or too few times have been fixed:
3864 C<$tied-E<gt>()> did not always call FETCH [perl #8438].
3868 Filetest operators and C<y///> and C<tr///> were calling FETCH too
3873 The C<=> operator used to ignore magic on its right-hand side if the
3874 scalar happened to hold a typeglob (if a typeglob was the last thing
3875 returned from or assigned to a tied scalar) [perl #77498].
3879 Dereference operators used to ignore magic if the argument was a
3880 reference already (e.g., from a previous FETCH) [perl #72144].
3884 C<splice> now calls set-magic (so changes made
3885 by C<splice @ISA> are respected by method calls) [perl #78400].
3889 In-memory files created by C<open $fh, 'E<gt>' \$buffer> were not calling
3890 FETCH/STORE at all [perl #43789] (5.12.2).
3894 utf8::is_utf8 now respects get-magic (e.g. $1) (5.12.1).
3900 String C<eval> now detects taintedness of overloaded or tied
3901 arguments [perl #75716].
3905 String C<eval> and regular expression matches against objects with string
3906 overloading no longer cause memory corruption or crashes [perl 77084].
3910 L<readline|perlfunc/"readline EXPR"> now honors C<< <> >> overloading on tied
3915 C<< E<lt>exprE<gt> >> always respects overloading now if the expression is
3918 Due to the way that 'E<lt>E<gt> as glob' was parsed differently from
3919 'E<lt>E<gt> as filehandle' from 5.6 onwards, something like C<< E<lt>$foo[0]E<gt> >> did
3920 not handle overloading, even if C<$foo[0]> was an overloaded object. This
3921 was contrary to the documentation for overload, and meant that C<< E<lt>E<gt> >>
3922 could not be used as a general overloaded iterator operator.
3926 The fallback behaviour of overloading on binary operators was asymmetric
3931 Magic applied to variables in the main package no longer affects other packages.
3932 See L</Magic variables outside the main package> above [perl #76138].
3936 Sometimes magic (ties, taintedness, etc.) attached to variables could cause
3937 an object to last longer than it should, or cause a crash if a tied
3938 variable were freed from within a tie method. These have been fixed
3943 DESTROY methods of objects implementing ties are no longer able to crash by
3944 accessing the tied variable through a weak reference [perl #86328].
3948 Fixed a regression of kill() when a match variable is used for the
3949 process ID to kill [perl #75812].
3953 C<$AUTOLOAD> used to remain tainted forever if it ever became tainted. Now
3954 it is correctly untainted if an autoloaded method is called and the method
3955 name was not tainted.
3959 C<sprintf> now dies when passed a tainted scalar for the format. It did
3960 already die for arbitrary expressions, but not for simple scalars
3965 C<lc>, C<uc>, C<lcfirst> and C<ucfirst> no longer return untainted strings
3966 when the argument is tainted. This has been broken since perl 5.8.9
3977 The Perl debugger now also works in taint mode [perl #76872].
3981 Subroutine redefinition works once more in the debugger [perl #48332].
3985 When C<-d> is used on the shebang (C<#!>) line, the debugger now has access
3986 to the lines of the main program. In the past, this sometimes worked and
3987 sometimes did not, depending on what order things happened to be arranged
3988 in memory [perl #71806].
3992 A possible memory leak when using L<caller()|perlfunc/"caller EXPR"> to set
3993 C<@DB::args> has been fixed (5.12.2).
3997 Perl no longer stomps on $DB::single, $DB::trace and $DB::signal if they
3998 already have values when $^P is assigned to [perl #72422].
4002 C<#line> directives in string evals were not properly updating the arrays
4003 of lines of code (C<< @{"_<..."} >>) that the debugger (or any debugging or
4004 profiling module) uses. In threaded builds, they were not being updated at
4005 all. In non-threaded builds, the line number was ignored, so any change to
4006 the existing line number would cause the lines to be misnumbered
4017 Perl no longer accidentally clones lexicals in scope within active stack
4018 frames in the parent when creating a child thread [perl #73086].
4022 Several memory leaks in cloning and freeing threaded Perl interpreters have been
4023 fixed [perl #77352].
4027 Creating a new thread when directory handles were open used to cause a
4028 crash, because the handles were not cloned, but simply passed to the new
4029 thread, resulting in a double free.
4031 Now directory handles are cloned properly, on Windows
4032 and on systems that have a C<fchdir> function. On other
4033 systems, new threads simply do not inherit directory
4034 handles from their parent threads [perl #75154].
4038 The typeglob C<*,>, which holds the scalar variable C<$,> (output field
4039 separator), had the wrong reference count in child threads.
4043 [perl #78494] When pipes are shared between threads, the C<close> function
4044 (and any implicit close, such as on thread exit) no longer blocks.
4048 Perl now does a timely cleanup of SVs that are cloned into a new thread but
4049 then discovered to be orphaned (i.e., their
4050 owners are I<not> cloned). This
4051 eliminates several "scalars leaked" warnings when joining threads.
4055 =head2 Scoping and Subroutines
4061 Lvalue subroutines are again able to return copy-on-write scalars. This
4062 had been broken since version 5.10.0 [perl #75656] (5.12.3).
4066 C<require> no longer causes C<caller> to return the wrong file name for
4067 the scope that called C<require> and other scopes higher up that had the
4068 same file name [perl #68712].
4072 C<sort> with a ($$)-prototyped comparison routine used to cause the value
4073 of @_ to leak out of the sort. Taking a reference to @_ within the
4074 sorting routine could cause a crash [perl #72334].
4078 Match variables (e.g., C<$1>) no longer persist between calls to a sort
4079 subroutine [perl #76026].
4083 Iterating with C<foreach> over an array returned by an lvalue sub now works
4088 C<$@> is now localised during calls to C<binmode> to prevent action at a
4089 distance [perl #78844].
4093 Calling a closure prototype (what is passed to an attribute handler for a
4094 closure) now results in a "Closure prototype called" error message instead
4095 of a crash [perl #68560].
4099 Mentioning a read-only lexical variable from the enclosing scope in a
4100 string C<eval> no longer causes the variable to become writable
4111 Within signal handlers, C<$!> is now implicitly localized.
4115 CHLD signals are no longer unblocked after a signal handler is called if
4116 they were blocked before by C<POSIX::sigprocmask> [perl #82040].
4120 A signal handler called within a signal handler could cause leaks or
4121 double-frees. Now fixed [perl #76248].
4125 =head2 Miscellaneous Memory Leaks
4131 Several memory leaks when loading XS modules were fixed (5.12.2).
4135 L<substr()|perlfunc/"substr EXPR,OFFSET,LENGTH,REPLACEMENT">,
4136 L<pos()|perlfunc/"index STR,SUBSTR,POSITION">, L<keys()|perlfunc/"keys HASH">,
4137 and L<vec()|perlfunc/"vec EXPR,OFFSET,BITS"> could, when used in combination
4138 with lvalues, result in leaking the scalar value they operate on, and cause its
4139 destruction to happen too late. This has now been fixed.
4143 The postincrement and postdecrement operators, C<++> and C<-->, used to cause
4144 leaks when being used on references. This has now been fixed.
4148 Nested C<map> and C<grep> blocks no longer leak memory when processing
4149 large lists [perl #48004].
4153 C<use I<VERSION>> and C<no I<VERSION>> no longer leak memory [perl #78436]
4158 C<.=> followed by C<< <> >> or C<readline> would leak memory if C<$/>
4159 contained characters beyond the octet range and the scalar assigned to
4160 happened to be encoded as UTF8 internally [perl #72246].
4164 C<eval "BEGIN{die}"> no longer leaks memory on non-threaded builds.
4168 =head2 Memory Corruption and Crashes
4174 glob() no longer crashes when %File::Glob:: is empty and
4175 CORE::GLOBAL::glob isn't present [perl #75464] (5.12.2).
4179 readline() has been fixed when interrupted by signals so it no longer
4180 returns the "same thing" as before or random memory.
4184 When assigning a list with duplicated keys to a hash, the assignment used to
4185 return garbage and/or freed values:
4187 @a = %h = (list with some duplicate keys);
4189 This has now been fixed [perl #31865].
4193 The mechanism for freeing objects in globs used to leave dangling
4194 pointers to freed SVs, meaning Perl users could see corrupted state
4197 Perl now only frees the affected slots of the GV, rather than freeing
4198 the GV itself. This makes sure that there are no dangling refs or
4199 corrupted state during destruction.
4203 The interpreter no longer crashes when freeing deeply-nested arrays of
4204 arrays. Hashes have not been fixed yet [perl #44225].
4208 Concatenating long strings under C<use encoding> no longer causes perl to
4209 crash [perl #78674].
4213 Calling C<< ->import >> on a class lacking an import method could corrupt
4214 the stack, resulting in strange behaviour. For instance,
4216 push @a, "foo", $b = bar->import;
4218 would assign 'foo' to C<$b> [perl #63790].
4222 The C<recv> function could crash when called with the MSG_TRUNC flag
4227 C<formline> no longer crashes when passed a tainted format picture. It also
4228 taints C<$^A> now if its arguments are tainted [perl #79138].
4232 A bug in how we process filetest operations could cause a segfault.
4233 Filetests don't always expect an op on the stack, so we now use
4234 TOPs only if we're sure that we're not stat'ing the _ filehandle.
4235 This is indicated by OPf_KIDS (as checked in ck_ftst) [perl #74542]
4240 C<unpack()> now handles scalar context correctly for C<%32H> and C<%32u>,
4241 fixing a potential crash. C<split()> would crash because the third item
4242 on the stack wasn't the regular expression it expected. C<unpack("%2H",
4243 ...)> would return both the unpacked result and the checksum on the stack,
4244 as would C<unpack("%2u", ...)> [perl #73814] (5.12.2).
4248 =head2 Fixes to Various Perl Operators
4254 The C<&> C<|> C<^> bitwise operators no longer coerce read-only arguments
4259 Stringifying a scalar containing -0.0 no longer has the affect of turning
4260 false into true [perl #45133].
4264 Some numeric operators were converting integers to floating point,
4265 resulting in loss of precision on 64-bit platforms [perl #77456].
4269 C<sprintf> was ignoring locales when called with constant arguments
4274 Combining the vector (%v) flag and dynamic precision would
4275 cause sprintf to confuse the order of its arguments, making it treat the
4276 string as the precision and vice versa [perl #83194].
4280 =head2 Bugs Relating to the C API
4286 The C-level C<lex_stuff_pvn> function would sometimes cause a spurious
4287 syntax error on the last line of the file if it lacked a final semicolon
4288 [perl #74006] (5.12.1).
4292 The C<eval_sv> and C<eval_pv> C functions now set C<$@> correctly when
4293 there is a syntax error and no C<G_KEEPERR> flag, and never set it if the
4294 C<G_KEEPERR> flag is present [perl #3719].
4298 The XS multicall API no longer causes subroutines to lose reference counts
4299 if called via the multicall interface from within those very subroutines.
4300 This affects modules like List::Util. Calling one of its functions with an
4301 active subroutine as the first argument could cause a crash [perl #78070].
4305 The C<SvPVbyte> function available to XS modules now calls magic before
4306 downgrading the SV, to avoid warnings about wide characters [perl #72398].
4310 The ref types in the typemap for XS bindings now support magical variables
4315 C<sv_catsv_flags> no longer calls C<mg_get> on its second argument (the
4316 source string) if the flags passed to it do not include SV_GMAGIC. So it
4317 now matches the documentation.
4321 C<my_strftime> no longer leaks memory. This fixes a memory leak in
4322 C<POSIX::strftime> [perl #73520].
4326 XSUB.h now correctly redefines fgets under PERL_IMPLICIT_SYS [perl #55049]
4331 XS code using C<fputc()> or C<fputs()>: on Windows could cause an error
4332 due to their arguments being swapped [perl #72704] (5.12.1).
4336 A possible segfault in the C<T_PRTOBJ> default typemap has been fixed
4341 A bug that could cause "Unknown error" messages when
4342 C<call_sv(code, G_EVAL)> is called from an XS destructor has been fixed
4347 =head1 Known Problems
4349 XXX Many of these have probably already been solved. There are also
4350 unresolved BBC articles linked to #77718 that are awaiting CPAN
4351 releases. These may need to be listed here.
4352 See also #84444. Enbugger may also need to be listed if there is no new
4353 release in time (see #82152).
4354 JJORE/overload-eval-0.08.tar.gz appears to be broken, too. See
4355 http://www.nntp.perl.org/group/perl.perl5.porters/2010/11/msg165773.html
4361 C<List::Util::first> misbehaves in the presence of a lexical C<$_>
4362 (typically introduced by C<my $_> or implicitly by C<given>). The variable
4363 which gets set for each iteration is the package variable C<$_>, not the
4366 A similar issue may occur in other modules that provide functions which
4367 take a block as their first argument, like
4369 foo { ... $_ ...} list
4371 See also: L<http://rt.perl.org/rt3/Public/Bug/Display.html?id=67694>
4375 readline() returns an empty string instead of undef when it is
4376 interrupted by a signal
4380 Test-Harness was updated from 3.17 to 3.21 for this release. A rewrite
4381 in how it handles non-Perl tests (in 3.17_01) broke argument passing to
4382 non-Perl tests with L<prove> (RT #59186), and required that non-Perl
4383 tests be run as C<prove ./test.sh> instead of C<prove test.sh> These
4384 issues are being solved upstream, but didn't make it into this release.
4385 They're expected to be fixed in time for perl v5.13.4. (RT #59457)
4389 C<version> now prevents object methods from being called as class methods
4394 The changes in L<substr()|perlfunc/"substr EXPR,OFFSET,LENGTH,REPLACEMENT">
4395 broke C<HTML::Parser> <= 3.66. A fixed C<HTML::Parser> is available as versions
4400 The changes in prototype handling break C<Switch>. A patch has been sent
4401 upstream and will hopefully appear on CPAN soon.
4405 The upgrade to Encode-2.40 has caused some tests in the libwww-perl distribution
4406 on CPAN to fail. (Specifically, F<base/message-charset.t> tests 33-36 in version
4407 5.836 of that distribution now fail.)
4411 The upgrade to ExtUtils-MakeMaker-6.57_05 has caused some tests in the
4412 Module-Install distribution on CPAN to fail. (Specifically, F<02_mymeta.t> tests
4413 5 and 21, F<18_all_from.t> tests 6 and 15, F<19_authors.t> tests 5, 13, 21 and
4414 29, and F<20_authors_with_special_characters.t> tests 6, 15 and 23 in version
4415 1.00 of that distribution now fail.)
4421 =head2 C<keys>, C<values> and C<each> work on arrays
4423 You can now use the C<keys>, C<values>, C<each> builtin functions on arrays
4424 (previously you could only use them on hashes). See L<perlfunc> for details.
4425 This is actually a change introduced in perl 5.12.0, but it was missed from
4426 that release's perldelta.
4428 =head2 C<split> and C<@_>
4430 C<split> no longer modifies C<@_> when called in scalar or void context.
4431 In void context it now produces a "Useless use of split" warning.
4432 This was also a perl 5.12.0 changed that missed the perldelta.
4436 Randy Kobes, creator of the kobesearch alternative to search.cpan.org and
4437 contributor/maintainer to several core Perl toolchain modules, passed away
4438 on September 18, 2010 after a battle with lung cancer. His contributions
4439 to the Perl community will be missed.
4441 =head1 Acknowledgements
4443 XXX The list of people to thank goes here.
4445 =head1 Reporting Bugs
4447 If you find what you think is a bug, you might check the articles
4448 recently posted to the comp.lang.perl.misc newsgroup and the perl
4449 bug database at http://rt.perl.org/perlbug/ . There may also be
4450 information at http://www.perl.org/ , the Perl Home Page.
4452 If you believe you have an unreported bug, please run the L<perlbug>
4453 program included with your release. Be sure to trim your bug down
4454 to a tiny but sufficient test case. Your bug report, along with the
4455 output of C<perl -V>, will be sent off to perlbug@perl.org to be
4456 analysed by the Perl porting team.
4458 If the bug you are reporting has security implications, which make it
4459 inappropriate to send to a publicly archived mailing list, then please send
4460 it to perl5-security-report@perl.org. This points to a closed subscription
4461 unarchived mailing list, which includes all the core committers, who be able
4462 to help assess the impact of issues, figure out a resolution, and help
4463 co-ordinate the release of patches to mitigate or fix the problem across all
4464 platforms on which Perl is supported. Please only use this address for
4465 security issues in the Perl core, not for modules independently
4466 distributed on CPAN.
4470 The F<Changes> file for an explanation of how to view exhaustive details
4473 The F<INSTALL> file for how to build Perl.
4475 The F<README> file for general stuff.
4477 The F<Artistic> and F<Copying> files for copyright information.