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diff --git a/Master/tlpkg/tlperl/lib/pods/perl5100delta.pod b/Master/tlpkg/tlperl/lib/pods/perl5100delta.pod new file mode 100644 index 00000000000..e93c316954a --- /dev/null +++ b/Master/tlpkg/tlperl/lib/pods/perl5100delta.pod @@ -0,0 +1,1612 @@ +=encoding utf8 + +=head1 NAME + +perl5100delta - what is new for perl 5.10.0 + +=head1 DESCRIPTION + +This document describes the differences between the 5.8.8 release and +the 5.10.0 release. + +Many of the bug fixes in 5.10.0 were already seen in the 5.8.X maintenance +releases; they are not duplicated here and are documented in the set of +man pages named perl58[1-8]?delta. + +=head1 Core Enhancements + +=head2 The C<feature> pragma + +The C<feature> pragma is used to enable new syntax that would break Perl's +backwards-compatibility with older releases of the language. It's a lexical +pragma, like C<strict> or C<warnings>. + +Currently the following new features are available: C<switch> (adds a +switch statement), C<say> (adds a C<say> built-in function), and C<state> +(adds a C<state> keyword for declaring "static" variables). Those +features are described in their own sections of this document. + +The C<feature> pragma is also implicitly loaded when you require a minimal +perl version (with the C<use VERSION> construct) greater than, or equal +to, 5.9.5. See L<feature> for details. + +=head2 New B<-E> command-line switch + +B<-E> is equivalent to B<-e>, but it implicitly enables all +optional features (like C<use feature ":5.10">). + +=head2 Defined-or operator + +A new operator C<//> (defined-or) has been implemented. +The following expression: + + $a // $b + +is merely equivalent to + + defined $a ? $a : $b + +and the statement + + $c //= $d; + +can now be used instead of + + $c = $d unless defined $c; + +The C<//> operator has the same precedence and associativity as C<||>. +Special care has been taken to ensure that this operator Do What You Mean +while not breaking old code, but some edge cases involving the empty +regular expression may now parse differently. See L<perlop> for +details. + +=head2 Switch and Smart Match operator + +Perl 5 now has a switch statement. It's available when C<use feature +'switch'> is in effect. This feature introduces three new keywords, +C<given>, C<when>, and C<default>: + + given ($foo) { + when (/^abc/) { $abc = 1; } + when (/^def/) { $def = 1; } + when (/^xyz/) { $xyz = 1; } + default { $nothing = 1; } + } + +A more complete description of how Perl matches the switch variable +against the C<when> conditions is given in L<perlsyn/"Switch statements">. + +This kind of match is called I<smart match>, and it's also possible to use +it outside of switch statements, via the new C<~~> operator. See +L<perlsyn/"Smart matching in detail">. + +This feature was contributed by Robin Houston. + +=head2 Regular expressions + +=over 4 + +=item Recursive Patterns + +It is now possible to write recursive patterns without using the C<(??{})> +construct. This new way is more efficient, and in many cases easier to +read. + +Each capturing parenthesis can now be treated as an independent pattern +that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for +"parenthesis number"). For example, the following pattern will match +nested balanced angle brackets: + + / + ^ # start of line + ( # start capture buffer 1 + < # match an opening angle bracket + (?: # match one of: + (?> # don't backtrack over the inside of this group + [^<>]+ # one or more non angle brackets + ) # end non backtracking group + | # ... or ... + (?1) # recurse to bracket 1 and try it again + )* # 0 or more times. + > # match a closing angle bracket + ) # end capture buffer one + $ # end of line + /x + +PCRE users should note that Perl's recursive regex feature allows +backtracking into a recursed pattern, whereas in PCRE the recursion is +atomic or "possessive" in nature. As in the example above, you can +add (?>) to control this selectively. (Yves Orton) + +=item Named Capture Buffers + +It is now possible to name capturing parenthesis in a pattern and refer to +the captured contents by name. The naming syntax is C<< (?<NAME>....) >>. +It's possible to backreference to a named buffer with the C<< \k<NAME> >> +syntax. In code, the new magical hashes C<%+> and C<%-> can be used to +access the contents of the capture buffers. + +Thus, to replace all doubled chars with a single copy, one could write + + s/(?<letter>.)\k<letter>/$+{letter}/g + +Only buffers with defined contents will be "visible" in the C<%+> hash, so +it's possible to do something like + + foreach my $name (keys %+) { + print "content of buffer '$name' is $+{$name}\n"; + } + +The C<%-> hash is a bit more complete, since it will contain array refs +holding values from all capture buffers similarly named, if there should +be many of them. + +C<%+> and C<%-> are implemented as tied hashes through the new module +C<Tie::Hash::NamedCapture>. + +Users exposed to the .NET regex engine will find that the perl +implementation differs in that the numerical ordering of the buffers +is sequential, and not "unnamed first, then named". Thus in the pattern + + /(A)(?<B>B)(C)(?<D>D)/ + +$1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not +$1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer +would expect. This is considered a feature. :-) (Yves Orton) + +=item Possessive Quantifiers + +Perl now supports the "possessive quantifier" syntax of the "atomic match" +pattern. Basically a possessive quantifier matches as much as it can and never +gives any back. Thus it can be used to control backtracking. The syntax is +similar to non-greedy matching, except instead of using a '?' as the modifier +the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal +quantifiers. (Yves Orton) + +=item Backtracking control verbs + +The regex engine now supports a number of special-purpose backtrack +control verbs: (*THEN), (*PRUNE), (*MARK), (*SKIP), (*COMMIT), (*FAIL) +and (*ACCEPT). See L<perlre> for their descriptions. (Yves Orton) + +=item Relative backreferences + +A new syntax C<\g{N}> or C<\gN> where "N" is a decimal integer allows a +safer form of back-reference notation as well as allowing relative +backreferences. This should make it easier to generate and embed patterns +that contain backreferences. See L<perlre/"Capture buffers">. (Yves Orton) + +=item C<\K> escape + +The functionality of Jeff Pinyan's module Regexp::Keep has been added to +the core. In regular expressions you can now use the special escape C<\K> +as a way to do something like floating length positive lookbehind. It is +also useful in substitutions like: + + s/(foo)bar/$1/g + +that can now be converted to + + s/foo\Kbar//g + +which is much more efficient. (Yves Orton) + +=item Vertical and horizontal whitespace, and linebreak + +Regular expressions now recognize the C<\v> and C<\h> escapes that match +vertical and horizontal whitespace, respectively. C<\V> and C<\H> +logically match their complements. + +C<\R> matches a generic linebreak, that is, vertical whitespace, plus +the multi-character sequence C<"\x0D\x0A">. + +=back + +=head2 C<say()> + +say() is a new built-in, only available when C<use feature 'say'> is in +effect, that is similar to print(), but that implicitly appends a newline +to the printed string. See L<perlfunc/say>. (Robin Houston) + +=head2 Lexical C<$_> + +The default variable C<$_> can now be lexicalized, by declaring it like +any other lexical variable, with a simple + + my $_; + +The operations that default on C<$_> will use the lexically-scoped +version of C<$_> when it exists, instead of the global C<$_>. + +In a C<map> or a C<grep> block, if C<$_> was previously my'ed, then the +C<$_> inside the block is lexical as well (and scoped to the block). + +In a scope where C<$_> has been lexicalized, you can still have access to +the global version of C<$_> by using C<$::_>, or, more simply, by +overriding the lexical declaration with C<our $_>. (Rafael Garcia-Suarez) + +=head2 The C<_> prototype + +A new prototype character has been added. C<_> is equivalent to C<$> but +defaults to C<$_> if the corresponding argument isn't supplied (both C<$> +and C<_> denote a scalar). Due to the optional nature of the argument, +you can only use it at the end of a prototype, or before a semicolon. + +This has a small incompatible consequence: the prototype() function has +been adjusted to return C<_> for some built-ins in appropriate cases (for +example, C<prototype('CORE::rmdir')>). (Rafael Garcia-Suarez) + +=head2 UNITCHECK blocks + +C<UNITCHECK>, a new special code block has been introduced, in addition to +C<BEGIN>, C<CHECK>, C<INIT> and C<END>. + +C<CHECK> and C<INIT> blocks, while useful for some specialized purposes, +are always executed at the transition between the compilation and the +execution of the main program, and thus are useless whenever code is +loaded at runtime. On the other hand, C<UNITCHECK> blocks are executed +just after the unit which defined them has been compiled. See L<perlmod> +for more information. (Alex Gough) + +=head2 New Pragma, C<mro> + +A new pragma, C<mro> (for Method Resolution Order) has been added. It +permits to switch, on a per-class basis, the algorithm that perl uses to +find inherited methods in case of a multiple inheritance hierarchy. The +default MRO hasn't changed (DFS, for Depth First Search). Another MRO is +available: the C3 algorithm. See L<mro> for more information. +(Brandon Black) + +Note that, due to changes in the implementation of class hierarchy search, +code that used to undef the C<*ISA> glob will most probably break. Anyway, +undef'ing C<*ISA> had the side-effect of removing the magic on the @ISA +array and should not have been done in the first place. Also, the +cache C<*::ISA::CACHE::> no longer exists; to force reset the @ISA cache, +you now need to use the C<mro> API, or more simply to assign to @ISA +(e.g. with C<@ISA = @ISA>). + +=head2 readdir() may return a "short filename" on Windows + +The readdir() function may return a "short filename" when the long +filename contains characters outside the ANSI codepage. Similarly +Cwd::cwd() may return a short directory name, and glob() may return short +names as well. On the NTFS file system these short names can always be +represented in the ANSI codepage. This will not be true for all other file +system drivers; e.g. the FAT filesystem stores short filenames in the OEM +codepage, so some files on FAT volumes remain unaccessible through the +ANSI APIs. + +Similarly, $^X, @INC, and $ENV{PATH} are preprocessed at startup to make +sure all paths are valid in the ANSI codepage (if possible). + +The Win32::GetLongPathName() function now returns the UTF-8 encoded +correct long file name instead of using replacement characters to force +the name into the ANSI codepage. The new Win32::GetANSIPathName() +function can be used to turn a long pathname into a short one only if the +long one cannot be represented in the ANSI codepage. + +Many other functions in the C<Win32> module have been improved to accept +UTF-8 encoded arguments. Please see L<Win32> for details. + +=head2 readpipe() is now overridable + +The built-in function readpipe() is now overridable. Overriding it permits +also to override its operator counterpart, C<qx//> (a.k.a. C<``>). +Moreover, it now defaults to C<$_> if no argument is provided. (Rafael +Garcia-Suarez) + +=head2 Default argument for readline() + +readline() now defaults to C<*ARGV> if no argument is provided. (Rafael +Garcia-Suarez) + +=head2 state() variables + +A new class of variables has been introduced. State variables are similar +to C<my> variables, but are declared with the C<state> keyword in place of +C<my>. They're visible only in their lexical scope, but their value is +persistent: unlike C<my> variables, they're not undefined at scope entry, +but retain their previous value. (Rafael Garcia-Suarez, Nicholas Clark) + +To use state variables, one needs to enable them by using + + use feature 'state'; + +or by using the C<-E> command-line switch in one-liners. +See L<perlsub/"Persistent Private Variables">. + +=head2 Stacked filetest operators + +As a new form of syntactic sugar, it's now possible to stack up filetest +operators. You can now write C<-f -w -x $file> in a row to mean +C<-x $file && -w _ && -f _>. See L<perlfunc/-X>. + +=head2 UNIVERSAL::DOES() + +The C<UNIVERSAL> class has a new method, C<DOES()>. It has been added to +solve semantic problems with the C<isa()> method. C<isa()> checks for +inheritance, while C<DOES()> has been designed to be overridden when +module authors use other types of relations between classes (in addition +to inheritance). (chromatic) + +See L<< UNIVERSAL/"$obj->DOES( ROLE )" >>. + +=head2 Formats + +Formats were improved in several ways. A new field, C<^*>, can be used for +variable-width, one-line-at-a-time text. Null characters are now handled +correctly in picture lines. Using C<@#> and C<~~> together will now +produce a compile-time error, as those format fields are incompatible. +L<perlform> has been improved, and miscellaneous bugs fixed. + +=head2 Byte-order modifiers for pack() and unpack() + +There are two new byte-order modifiers, C<E<gt>> (big-endian) and C<E<lt>> +(little-endian), that can be appended to most pack() and unpack() template +characters and groups to force a certain byte-order for that type or group. +See L<perlfunc/pack> and L<perlpacktut> for details. + +=head2 C<no VERSION> + +You can now use C<no> followed by a version number to specify that you +want to use a version of perl older than the specified one. + +=head2 C<chdir>, C<chmod> and C<chown> on filehandles + +C<chdir>, C<chmod> and C<chown> can now work on filehandles as well as +filenames, if the system supports respectively C<fchdir>, C<fchmod> and +C<fchown>, thanks to a patch provided by Gisle Aas. + +=head2 OS groups + +C<$(> and C<$)> now return groups in the order where the OS returns them, +thanks to Gisle Aas. This wasn't previously the case. + +=head2 Recursive sort subs + +You can now use recursive subroutines with sort(), thanks to Robin Houston. + +=head2 Exceptions in constant folding + +The constant folding routine is now wrapped in an exception handler, and +if folding throws an exception (such as attempting to evaluate 0/0), perl +now retains the current optree, rather than aborting the whole program. +Without this change, programs would not compile if they had expressions that +happened to generate exceptions, even though those expressions were in code +that could never be reached at runtime. (Nicholas Clark, Dave Mitchell) + +=head2 Source filters in @INC + +It's possible to enhance the mechanism of subroutine hooks in @INC by +adding a source filter on top of the filehandle opened and returned by the +hook. This feature was planned a long time ago, but wasn't quite working +until now. See L<perlfunc/require> for details. (Nicholas Clark) + +=head2 New internal variables + +=over 4 + +=item C<${^RE_DEBUG_FLAGS}> + +This variable controls what debug flags are in effect for the regular +expression engine when running under C<use re "debug">. See L<re> for +details. + +=item C<${^CHILD_ERROR_NATIVE}> + +This variable gives the native status returned by the last pipe close, +backtick command, successful call to wait() or waitpid(), or from the +system() operator. See L<perlvar> for details. (Contributed by Gisle Aas.) + +=item C<${^RE_TRIE_MAXBUF}> + +See L</"Trie optimisation of literal string alternations">. + +=item C<${^WIN32_SLOPPY_STAT}> + +See L</"Sloppy stat on Windows">. + +=back + +=head2 Miscellaneous + +C<unpack()> now defaults to unpacking the C<$_> variable. + +C<mkdir()> without arguments now defaults to C<$_>. + +The internal dump output has been improved, so that non-printable characters +such as newline and backspace are output in C<\x> notation, rather than +octal. + +The B<-C> option can no longer be used on the C<#!> line. It wasn't +working there anyway, since the standard streams are already set up +at this point in the execution of the perl interpreter. You can use +binmode() instead to get the desired behaviour. + +=head2 UCD 5.0.0 + +The copy of the Unicode Character Database included in Perl 5 has +been updated to version 5.0.0. + +=head2 MAD + +MAD, which stands for I<Miscellaneous Attribute Decoration>, is a +still-in-development work leading to a Perl 5 to Perl 6 converter. To +enable it, it's necessary to pass the argument C<-Dmad> to Configure. The +obtained perl isn't binary compatible with a regular perl 5.10, and has +space and speed penalties; moreover not all regression tests still pass +with it. (Larry Wall, Nicholas Clark) + +=head2 kill() on Windows + +On Windows platforms, C<kill(-9, $pid)> now kills a process tree. +(On Unix, this delivers the signal to all processes in the same process +group.) + +=head1 Incompatible Changes + +=head2 Packing and UTF-8 strings + +The semantics of pack() and unpack() regarding UTF-8-encoded data has been +changed. Processing is now by default character per character instead of +byte per byte on the underlying encoding. Notably, code that used things +like C<pack("a*", $string)> to see through the encoding of string will now +simply get back the original $string. Packed strings can also get upgraded +during processing when you store upgraded characters. You can get the old +behaviour by using C<use bytes>. + +To be consistent with pack(), the C<C0> in unpack() templates indicates +that the data is to be processed in character mode, i.e. character by +character; on the contrary, C<U0> in unpack() indicates UTF-8 mode, where +the packed string is processed in its UTF-8-encoded Unicode form on a byte +by byte basis. This is reversed with regard to perl 5.8.X, but now consistent +between pack() and unpack(). + +Moreover, C<C0> and C<U0> can also be used in pack() templates to specify +respectively character and byte modes. + +C<C0> and C<U0> in the middle of a pack or unpack format now switch to the +specified encoding mode, honoring parens grouping. Previously, parens were +ignored. + +Also, there is a new pack() character format, C<W>, which is intended to +replace the old C<C>. C<C> is kept for unsigned chars coded as bytes in +the strings internal representation. C<W> represents unsigned (logical) +character values, which can be greater than 255. It is therefore more +robust when dealing with potentially UTF-8-encoded data (as C<C> will wrap +values outside the range 0..255, and not respect the string encoding). + +In practice, that means that pack formats are now encoding-neutral, except +C<C>. + +For consistency, C<A> in unpack() format now trims all Unicode whitespace +from the end of the string. Before perl 5.9.2, it used to strip only the +classical ASCII space characters. + +=head2 Byte/character count feature in unpack() + +A new unpack() template character, C<".">, returns the number of bytes or +characters (depending on the selected encoding mode, see above) read so far. + +=head2 The C<$*> and C<$#> variables have been removed + +C<$*>, which was deprecated in favor of the C</s> and C</m> regexp +modifiers, has been removed. + +The deprecated C<$#> variable (output format for numbers) has been +removed. + +Two new severe warnings, C<$#/$* is no longer supported>, have been added. + +=head2 substr() lvalues are no longer fixed-length + +The lvalues returned by the three argument form of substr() used to be a +"fixed length window" on the original string. In some cases this could +cause surprising action at distance or other undefined behaviour. Now the +length of the window adjusts itself to the length of the string assigned to +it. + +=head2 Parsing of C<-f _> + +The identifier C<_> is now forced to be a bareword after a filetest +operator. This solves a number of misparsing issues when a global C<_> +subroutine is defined. + +=head2 C<:unique> + +The C<:unique> attribute has been made a no-op, since its current +implementation was fundamentally flawed and not threadsafe. + +=head2 Effect of pragmas in eval + +The compile-time value of the C<%^H> hint variable can now propagate into +eval("")uated code. This makes it more useful to implement lexical +pragmas. + +As a side-effect of this, the overloaded-ness of constants now propagates +into eval(""). + +=head2 chdir FOO + +A bareword argument to chdir() is now recognized as a file handle. +Earlier releases interpreted the bareword as a directory name. +(Gisle Aas) + +=head2 Handling of .pmc files + +An old feature of perl was that before C<require> or C<use> look for a +file with a F<.pm> extension, they will first look for a similar filename +with a F<.pmc> extension. If this file is found, it will be loaded in +place of any potentially existing file ending in a F<.pm> extension. + +Previously, F<.pmc> files were loaded only if more recent than the +matching F<.pm> file. Starting with 5.9.4, they'll be always loaded if +they exist. + +=head2 $^V is now a C<version> object instead of a v-string + +$^V can still be used with the C<%vd> format in printf, but any +character-level operations will now access the string representation +of the C<version> object and not the ordinals of a v-string. +Expressions like C<< substr($^V, 0, 2) >> or C<< split //, $^V >> +no longer work and must be rewritten. + +=head2 @- and @+ in patterns + +The special arrays C<@-> and C<@+> are no longer interpolated in regular +expressions. (Sadahiro Tomoyuki) + +=head2 $AUTOLOAD can now be tainted + +If you call a subroutine by a tainted name, and if it defers to an +AUTOLOAD function, then $AUTOLOAD will be (correctly) tainted. +(Rick Delaney) + +=head2 Tainting and printf + +When perl is run under taint mode, C<printf()> and C<sprintf()> will now +reject any tainted format argument. (Rafael Garcia-Suarez) + +=head2 undef and signal handlers + +Undefining or deleting a signal handler via C<undef $SIG{FOO}> is now +equivalent to setting it to C<'DEFAULT'>. (Rafael Garcia-Suarez) + +=head2 strictures and dereferencing in defined() + +C<use strict 'refs'> was ignoring taking a hard reference in an argument +to defined(), as in : + + use strict 'refs'; + my $x = 'foo'; + if (defined $$x) {...} + +This now correctly produces the run-time error C<Can't use string as a +SCALAR ref while "strict refs" in use>. + +C<defined @$foo> and C<defined %$bar> are now also subject to C<strict +'refs'> (that is, C<$foo> and C<$bar> shall be proper references there.) +(C<defined(@foo)> and C<defined(%bar)> are discouraged constructs anyway.) +(Nicholas Clark) + +=head2 C<(?p{})> has been removed + +The regular expression construct C<(?p{})>, which was deprecated in perl +5.8, has been removed. Use C<(??{})> instead. (Rafael Garcia-Suarez) + +=head2 Pseudo-hashes have been removed + +Support for pseudo-hashes has been removed from Perl 5.9. (The C<fields> +pragma remains here, but uses an alternate implementation.) + +=head2 Removal of the bytecode compiler and of perlcc + +C<perlcc>, the byteloader and the supporting modules (B::C, B::CC, +B::Bytecode, etc.) are no longer distributed with the perl sources. Those +experimental tools have never worked reliably, and, due to the lack of +volunteers to keep them in line with the perl interpreter developments, it +was decided to remove them instead of shipping a broken version of those. +The last version of those modules can be found with perl 5.9.4. + +However the B compiler framework stays supported in the perl core, as with +the more useful modules it has permitted (among others, B::Deparse and +B::Concise). + +=head2 Removal of the JPL + +The JPL (Java-Perl Lingo) has been removed from the perl sources tarball. + +=head2 Recursive inheritance detected earlier + +Perl will now immediately throw an exception if you modify any package's +C<@ISA> in such a way that it would cause recursive inheritance. + +Previously, the exception would not occur until Perl attempted to make +use of the recursive inheritance while resolving a method or doing a +C<$foo-E<gt>isa($bar)> lookup. + +=head2 warnings::enabled and warnings::warnif changed to favor users of modules + +The behaviour in 5.10.x favors the person using the module; +The behaviour in 5.8.x favors the module writer; + +Assume the following code: + + main calls Foo::Bar::baz() + Foo::Bar inherits from Foo::Base + Foo::Bar::baz() calls Foo::Base::_bazbaz() + Foo::Base::_bazbaz() calls: warnings::warnif('substr', 'some warning +message'); + +On 5.8.x, the code warns when Foo::Bar contains C<use warnings;> +It does not matter if Foo::Base or main have warnings enabled +to disable the warning one has to modify Foo::Bar. + +On 5.10.0 and newer, the code warns when main contains C<use warnings;> +It does not matter if Foo::Base or Foo::Bar have warnings enabled +to disable the warning one has to modify main. + +=head1 Modules and Pragmata + +=head2 Upgrading individual core modules + +Even more core modules are now also available separately through the +CPAN. If you wish to update one of these modules, you don't need to +wait for a new perl release. From within the cpan shell, running the +'r' command will report on modules with upgrades available. See +C<perldoc CPAN> for more information. + +=head2 Pragmata Changes + +=over 4 + +=item C<feature> + +The new pragma C<feature> is used to enable new features that might break +old code. See L</"The C<feature> pragma"> above. + +=item C<mro> + +This new pragma enables to change the algorithm used to resolve inherited +methods. See L</"New Pragma, C<mro>"> above. + +=item Scoping of the C<sort> pragma + +The C<sort> pragma is now lexically scoped. Its effect used to be global. + +=item Scoping of C<bignum>, C<bigint>, C<bigrat> + +The three numeric pragmas C<bignum>, C<bigint> and C<bigrat> are now +lexically scoped. (Tels) + +=item C<base> + +The C<base> pragma now warns if a class tries to inherit from itself. +(Curtis "Ovid" Poe) + +=item C<strict> and C<warnings> + +C<strict> and C<warnings> will now complain loudly if they are loaded via +incorrect casing (as in C<use Strict;>). (Johan Vromans) + +=item C<version> + +The C<version> module provides support for version objects. + +=item C<warnings> + +The C<warnings> pragma doesn't load C<Carp> anymore. That means that code +that used C<Carp> routines without having loaded it at compile time might +need to be adjusted; typically, the following (faulty) code won't work +anymore, and will require parentheses to be added after the function name: + + use warnings; + require Carp; + Carp::confess 'argh'; + +=item C<less> + +C<less> now does something useful (or at least it tries to). In fact, it +has been turned into a lexical pragma. So, in your modules, you can now +test whether your users have requested to use less CPU, or less memory, +less magic, or maybe even less fat. See L<less> for more. (Joshua ben +Jore) + +=back + +=head2 New modules + +=over 4 + +=item * + +C<encoding::warnings>, by Audrey Tang, is a module to emit warnings +whenever an ASCII character string containing high-bit bytes is implicitly +converted into UTF-8. It's a lexical pragma since Perl 5.9.4; on older +perls, its effect is global. + +=item * + +C<Module::CoreList>, by Richard Clamp, is a small handy module that tells +you what versions of core modules ship with any versions of Perl 5. It +comes with a command-line frontend, C<corelist>. + +=item * + +C<Math::BigInt::FastCalc> is an XS-enabled, and thus faster, version of +C<Math::BigInt::Calc>. + +=item * + +C<Compress::Zlib> is an interface to the zlib compression library. It +comes with a bundled version of zlib, so having a working zlib is not a +prerequisite to install it. It's used by C<Archive::Tar> (see below). + +=item * + +C<IO::Zlib> is an C<IO::>-style interface to C<Compress::Zlib>. + +=item * + +C<Archive::Tar> is a module to manipulate C<tar> archives. + +=item * + +C<Digest::SHA> is a module used to calculate many types of SHA digests, +has been included for SHA support in the CPAN module. + +=item * + +C<ExtUtils::CBuilder> and C<ExtUtils::ParseXS> have been added. + +=item * + +C<Hash::Util::FieldHash>, by Anno Siegel, has been added. This module +provides support for I<field hashes>: hashes that maintain an association +of a reference with a value, in a thread-safe garbage-collected way. +Such hashes are useful to implement inside-out objects. + +=item * + +C<Module::Build>, by Ken Williams, has been added. It's an alternative to +C<ExtUtils::MakeMaker> to build and install perl modules. + +=item * + +C<Module::Load>, by Jos Boumans, has been added. It provides a single +interface to load Perl modules and F<.pl> files. + +=item * + +C<Module::Loaded>, by Jos Boumans, has been added. It's used to mark +modules as loaded or unloaded. + +=item * + +C<Package::Constants>, by Jos Boumans, has been added. It's a simple +helper to list all constants declared in a given package. + +=item * + +C<Win32API::File>, by Tye McQueen, has been added (for Windows builds). +This module provides low-level access to Win32 system API calls for +files/dirs. + +=item * + +C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around +C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't +included in the perl core; the behaviour of C<Locale::Maketext::Simple> +gracefully degrades when the later isn't present. + +=item * + +C<Params::Check> implements a generic input parsing/checking mechanism. It +is used by CPANPLUS. + +=item * + +C<Term::UI> simplifies the task to ask questions at a terminal prompt. + +=item * + +C<Object::Accessor> provides an interface to create per-object accessors. + +=item * + +C<Module::Pluggable> is a simple framework to create modules that accept +pluggable sub-modules. + +=item * + +C<Module::Load::Conditional> provides simple ways to query and possibly +load installed modules. + +=item * + +C<Time::Piece> provides an object oriented interface to time functions, +overriding the built-ins localtime() and gmtime(). + +=item * + +C<IPC::Cmd> helps to find and run external commands, possibly +interactively. + +=item * + +C<File::Fetch> provide a simple generic file fetching mechanism. + +=item * + +C<Log::Message> and C<Log::Message::Simple> are used by the log facility +of C<CPANPLUS>. + +=item * + +C<Archive::Extract> is a generic archive extraction mechanism +for F<.tar> (plain, gziped or bzipped) or F<.zip> files. + +=item * + +C<CPANPLUS> provides an API and a command-line tool to access the CPAN +mirrors. + +=item * + +C<Pod::Escapes> provides utilities that are useful in decoding Pod +EE<lt>...E<gt> sequences. + +=item * + +C<Pod::Simple> is now the backend for several of the Pod-related modules +included with Perl. + +=back + +=head2 Selected Changes to Core Modules + +=over 4 + +=item C<Attribute::Handlers> + +C<Attribute::Handlers> can now report the caller's file and line number. +(David Feldman) + +All interpreted attributes are now passed as array references. (Damian +Conway) + +=item C<B::Lint> + +C<B::Lint> is now based on C<Module::Pluggable>, and so can be extended +with plugins. (Joshua ben Jore) + +=item C<B> + +It's now possible to access the lexical pragma hints (C<%^H>) by using the +method B::COP::hints_hash(). It returns a C<B::RHE> object, which in turn +can be used to get a hash reference via the method B::RHE::HASH(). (Joshua +ben Jore) + +=item C<Thread> + +As the old 5005thread threading model has been removed, in favor of the +ithreads scheme, the C<Thread> module is now a compatibility wrapper, to +be used in old code only. It has been removed from the default list of +dynamic extensions. + +=back + +=head1 Utility Changes + +=over 4 + +=item perl -d + +The Perl debugger can now save all debugger commands for sourcing later; +notably, it can now emulate stepping backwards, by restarting and +rerunning all bar the last command from a saved command history. + +It can also display the parent inheritance tree of a given class, with the +C<i> command. + +=item ptar + +C<ptar> is a pure perl implementation of C<tar> that comes with +C<Archive::Tar>. + +=item ptardiff + +C<ptardiff> is a small utility used to generate a diff between the contents +of a tar archive and a directory tree. Like C<ptar>, it comes with +C<Archive::Tar>. + +=item shasum + +C<shasum> is a command-line utility, used to print or to check SHA +digests. It comes with the new C<Digest::SHA> module. + +=item corelist + +The C<corelist> utility is now installed with perl (see L</"New modules"> +above). + +=item h2ph and h2xs + +C<h2ph> and C<h2xs> have been made more robust with regard to +"modern" C code. + +C<h2xs> implements a new option C<--use-xsloader> to force use of +C<XSLoader> even in backwards compatible modules. + +The handling of authors' names that had apostrophes has been fixed. + +Any enums with negative values are now skipped. + +=item perlivp + +C<perlivp> no longer checks for F<*.ph> files by default. Use the new C<-a> +option to run I<all> tests. + +=item find2perl + +C<find2perl> now assumes C<-print> as a default action. Previously, it +needed to be specified explicitly. + +Several bugs have been fixed in C<find2perl>, regarding C<-exec> and +C<-eval>. Also the options C<-path>, C<-ipath> and C<-iname> have been +added. + +=item config_data + +C<config_data> is a new utility that comes with C<Module::Build>. It +provides a command-line interface to the configuration of Perl modules +that use Module::Build's framework of configurability (that is, +C<*::ConfigData> modules that contain local configuration information for +their parent modules.) + +=item cpanp + +C<cpanp>, the CPANPLUS shell, has been added. (C<cpanp-run-perl>, a +helper for CPANPLUS operation, has been added too, but isn't intended for +direct use). + +=item cpan2dist + +C<cpan2dist> is a new utility that comes with CPANPLUS. It's a tool to +create distributions (or packages) from CPAN modules. + +=item pod2html + +The output of C<pod2html> has been enhanced to be more customizable via +CSS. Some formatting problems were also corrected. (Jari Aalto) + +=back + +=head1 New Documentation + +The L<perlpragma> manpage documents how to write one's own lexical +pragmas in pure Perl (something that is possible starting with 5.9.4). + +The new L<perlglossary> manpage is a glossary of terms used in the Perl +documentation, technical and otherwise, kindly provided by O'Reilly Media, +Inc. + +The L<perlreguts> manpage, courtesy of Yves Orton, describes internals of the +Perl regular expression engine. + +The L<perlreapi> manpage describes the interface to the perl interpreter +used to write pluggable regular expression engines (by Ævar Arnfjörð +Bjarmason). + +The L<perlunitut> manpage is an tutorial for programming with Unicode and +string encodings in Perl, courtesy of Juerd Waalboer. + +A new manual page, L<perlunifaq> (the Perl Unicode FAQ), has been added +(Juerd Waalboer). + +The L<perlcommunity> manpage gives a description of the Perl community +on the Internet and in real life. (Edgar "Trizor" Bering) + +The L<CORE> manual page documents the C<CORE::> namespace. (Tels) + +The long-existing feature of C</(?{...})/> regexps setting C<$_> and pos() +is now documented. + +=head1 Performance Enhancements + +=head2 In-place sorting + +Sorting arrays in place (C<@a = sort @a>) is now optimized to avoid +making a temporary copy of the array. + +Likewise, C<reverse sort ...> is now optimized to sort in reverse, +avoiding the generation of a temporary intermediate list. + +=head2 Lexical array access + +Access to elements of lexical arrays via a numeric constant between 0 and +255 is now faster. (This used to be only the case for global arrays.) + +=head2 XS-assisted SWASHGET + +Some pure-perl code that perl was using to retrieve Unicode properties and +transliteration mappings has been reimplemented in XS. + +=head2 Constant subroutines + +The interpreter internals now support a far more memory efficient form of +inlineable constants. Storing a reference to a constant value in a symbol +table is equivalent to a full typeglob referencing a constant subroutine, +but using about 400 bytes less memory. This proxy constant subroutine is +automatically upgraded to a real typeglob with subroutine if necessary. +The approach taken is analogous to the existing space optimisation for +subroutine stub declarations, which are stored as plain scalars in place +of the full typeglob. + +Several of the core modules have been converted to use this feature for +their system dependent constants - as a result C<use POSIX;> now takes about +200K less memory. + +=head2 C<PERL_DONT_CREATE_GVSV> + +The new compilation flag C<PERL_DONT_CREATE_GVSV>, introduced as an option +in perl 5.8.8, is turned on by default in perl 5.9.3. It prevents perl +from creating an empty scalar with every new typeglob. See L<perl589delta> +for details. + +=head2 Weak references are cheaper + +Weak reference creation is now I<O(1)> rather than I<O(n)>, courtesy of +Nicholas Clark. Weak reference deletion remains I<O(n)>, but if deletion only +happens at program exit, it may be skipped completely. + +=head2 sort() enhancements + +Salvador Fandiño provided improvements to reduce the memory usage of C<sort> +and to speed up some cases. + +=head2 Memory optimisations + +Several internal data structures (typeglobs, GVs, CVs, formats) have been +restructured to use less memory. (Nicholas Clark) + +=head2 UTF-8 cache optimisation + +The UTF-8 caching code is now more efficient, and used more often. +(Nicholas Clark) + +=head2 Sloppy stat on Windows + +On Windows, perl's stat() function normally opens the file to determine +the link count and update attributes that may have been changed through +hard links. Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up +stat() by not performing this operation. (Jan Dubois) + +=head2 Regular expressions optimisations + +=over 4 + +=item Engine de-recursivised + +The regular expression engine is no longer recursive, meaning that +patterns that used to overflow the stack will either die with useful +explanations, or run to completion, which, since they were able to blow +the stack before, will likely take a very long time to happen. If you were +experiencing the occasional stack overflow (or segfault) and upgrade to +discover that now perl apparently hangs instead, look for a degenerate +regex. (Dave Mitchell) + +=item Single char char-classes treated as literals + +Classes of a single character are now treated the same as if the character +had been used as a literal, meaning that code that uses char-classes as an +escaping mechanism will see a speedup. (Yves Orton) + +=item Trie optimisation of literal string alternations + +Alternations, where possible, are optimised into more efficient matching +structures. String literal alternations are merged into a trie and are +matched simultaneously. This means that instead of O(N) time for matching +N alternations at a given point, the new code performs in O(1) time. +A new special variable, ${^RE_TRIE_MAXBUF}, has been added to fine-tune +this optimization. (Yves Orton) + +B<Note:> Much code exists that works around perl's historic poor +performance on alternations. Often the tricks used to do so will disable +the new optimisations. Hopefully the utility modules used for this purpose +will be educated about these new optimisations. + +=item Aho-Corasick start-point optimisation + +When a pattern starts with a trie-able alternation and there aren't +better optimisations available, the regex engine will use Aho-Corasick +matching to find the start point. (Yves Orton) + +=back + +=head1 Installation and Configuration Improvements + +=head2 Configuration improvements + +=over 4 + +=item C<-Dusesitecustomize> + +Run-time customization of @INC can be enabled by passing the +C<-Dusesitecustomize> flag to Configure. When enabled, this will make perl +run F<$sitelibexp/sitecustomize.pl> before anything else. This script can +then be set up to add additional entries to @INC. + +=item Relocatable installations + +There is now Configure support for creating a relocatable perl tree. If +you Configure with C<-Duserelocatableinc>, then the paths in @INC (and +everything else in %Config) can be optionally located via the path of the +perl executable. + +That means that, if the string C<".../"> is found at the start of any +path, it's substituted with the directory of $^X. So, the relocation can +be configured on a per-directory basis, although the default with +C<-Duserelocatableinc> is that everything is relocated. The initial +install is done to the original configured prefix. + +=item strlcat() and strlcpy() + +The configuration process now detects whether strlcat() and strlcpy() are +available. When they are not available, perl's own version is used (from +Russ Allbery's public domain implementation). Various places in the perl +interpreter now use them. (Steve Peters) + +=item C<d_pseudofork> and C<d_printf_format_null> + +A new configuration variable, available as C<$Config{d_pseudofork}> in +the L<Config> module, has been added, to distinguish real fork() support +from fake pseudofork used on Windows platforms. + +A new configuration variable, C<d_printf_format_null>, has been added, +to see if printf-like formats are allowed to be NULL. + +=item Configure help + +C<Configure -h> has been extended with the most commonly used options. + +=back + +=head2 Compilation improvements + +=over 4 + +=item Parallel build + +Parallel makes should work properly now, although there may still be problems +if C<make test> is instructed to run in parallel. + +=item Borland's compilers support + +Building with Borland's compilers on Win32 should work more smoothly. In +particular Steve Hay has worked to side step many warnings emitted by their +compilers and at least one C compiler internal error. + +=item Static build on Windows + +Perl extensions on Windows now can be statically built into the Perl DLL. + +Also, it's now possible to build a C<perl-static.exe> that doesn't depend +on the Perl DLL on Win32. See the Win32 makefiles for details. +(Vadim Konovalov) + +=item ppport.h files + +All F<ppport.h> files in the XS modules bundled with perl are now +autogenerated at build time. (Marcus Holland-Moritz) + +=item C++ compatibility + +Efforts have been made to make perl and the core XS modules compilable +with various C++ compilers (although the situation is not perfect with +some of the compilers on some of the platforms tested.) + +=item Support for Microsoft 64-bit compiler + +Support for building perl with Microsoft's 64-bit compiler has been +improved. (ActiveState) + +=item Visual C++ + +Perl can now be compiled with Microsoft Visual C++ 2005 (and 2008 Beta 2). + +=item Win32 builds + +All win32 builds (MS-Win, WinCE) have been merged and cleaned up. + +=back + +=head2 Installation improvements + +=over 4 + +=item Module auxiliary files + +README files and changelogs for CPAN modules bundled with perl are no +longer installed. + +=back + +=head2 New Or Improved Platforms + +Perl has been reported to work on Symbian OS. See L<perlsymbian> for more +information. + +Many improvements have been made towards making Perl work correctly on +z/OS. + +Perl has been reported to work on DragonFlyBSD and MidnightBSD. + +Perl has also been reported to work on NexentaOS +( http://www.gnusolaris.org/ ). + +The VMS port has been improved. See L<perlvms>. + +Support for Cray XT4 Catamount/Qk has been added. See +F<hints/catamount.sh> in the source code distribution for more +information. + +Vendor patches have been merged for RedHat and Gentoo. + +DynaLoader::dl_unload_file() now works on Windows. + +=head1 Selected Bug Fixes + +=over 4 + +=item strictures in regexp-eval blocks + +C<strict> wasn't in effect in regexp-eval blocks (C</(?{...})/>). + +=item Calling CORE::require() + +CORE::require() and CORE::do() were always parsed as require() and do() +when they were overridden. This is now fixed. + +=item Subscripts of slices + +You can now use a non-arrowed form for chained subscripts after a list +slice, like in: + + ({foo => "bar"})[0]{foo} + +This used to be a syntax error; a C<< -> >> was required. + +=item C<no warnings 'category'> works correctly with -w + +Previously when running with warnings enabled globally via C<-w>, selective +disabling of specific warning categories would actually turn off all warnings. +This is now fixed; now C<no warnings 'io';> will only turn off warnings in the +C<io> class. Previously it would erroneously turn off all warnings. + +=item threads improvements + +Several memory leaks in ithreads were closed. Also, ithreads were made +less memory-intensive. + +C<threads> is now a dual-life module, also available on CPAN. It has been +expanded in many ways. A kill() method is available for thread signalling. +One can get thread status, or the list of running or joinable threads. + +A new C<< threads->exit() >> method is used to exit from the application +(this is the default for the main thread) or from the current thread only +(this is the default for all other threads). On the other hand, the exit() +built-in now always causes the whole application to terminate. (Jerry +D. Hedden) + +=item chr() and negative values + +chr() on a negative value now gives C<\x{FFFD}>, the Unicode replacement +character, unless when the C<bytes> pragma is in effect, where the low +eight bits of the value are used. + +=item PERL5SHELL and tainting + +On Windows, the PERL5SHELL environment variable is now checked for +taintedness. (Rafael Garcia-Suarez) + +=item Using *FILE{IO} + +C<stat()> and C<-X> filetests now treat *FILE{IO} filehandles like *FILE +filehandles. (Steve Peters) + +=item Overloading and reblessing + +Overloading now works when references are reblessed into another class. +Internally, this has been implemented by moving the flag for "overloading" +from the reference to the referent, which logically is where it should +always have been. (Nicholas Clark) + +=item Overloading and UTF-8 + +A few bugs related to UTF-8 handling with objects that have +stringification overloaded have been fixed. (Nicholas Clark) + +=item eval memory leaks fixed + +Traditionally, C<eval 'syntax error'> has leaked badly. Many (but not all) +of these leaks have now been eliminated or reduced. (Dave Mitchell) + +=item Random device on Windows + +In previous versions, perl would read the file F</dev/urandom> if it +existed when seeding its random number generator. That file is unlikely +to exist on Windows, and if it did would probably not contain appropriate +data, so perl no longer tries to read it on Windows. (Alex Davies) + +=item PERLIO_DEBUG + +The C<PERLIO_DEBUG> environment variable no longer has any effect for +setuid scripts and for scripts run with B<-T>. + +Moreover, with a thread-enabled perl, using C<PERLIO_DEBUG> could lead to +an internal buffer overflow. This has been fixed. + +=item PerlIO::scalar and read-only scalars + +PerlIO::scalar will now prevent writing to read-only scalars. Moreover, +seek() is now supported with PerlIO::scalar-based filehandles, the +underlying string being zero-filled as needed. (Rafael, Jarkko Hietaniemi) + +=item study() and UTF-8 + +study() never worked for UTF-8 strings, but could lead to false results. +It's now a no-op on UTF-8 data. (Yves Orton) + +=item Critical signals + +The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an +"unsafe" manner (contrary to other signals, that are deferred until the +perl interpreter reaches a reasonably stable state; see +L<perlipc/"Deferred Signals (Safe Signals)">). (Rafael) + +=item @INC-hook fix + +When a module or a file is loaded through an @INC-hook, and when this hook +has set a filename entry in %INC, __FILE__ is now set for this module +accordingly to the contents of that %INC entry. (Rafael) + +=item C<-t> switch fix + +The C<-w> and C<-t> switches can now be used together without messing +up which categories of warnings are activated. (Rafael) + +=item Duping UTF-8 filehandles + +Duping a filehandle which has the C<:utf8> PerlIO layer set will now +properly carry that layer on the duped filehandle. (Rafael) + +=item Localisation of hash elements + +Localizing a hash element whose key was given as a variable didn't work +correctly if the variable was changed while the local() was in effect (as +in C<local $h{$x}; ++$x>). (Bo Lindbergh) + +=back + +=head1 New or Changed Diagnostics + +=over 4 + +=item Use of uninitialized value + +Perl will now try to tell you the name of the variable (if any) that was +undefined. + +=item Deprecated use of my() in false conditional + +A new deprecation warning, I<Deprecated use of my() in false conditional>, +has been added, to warn against the use of the dubious and deprecated +construct + + my $x if 0; + +See L<perldiag>. Use C<state> variables instead. + +=item !=~ should be !~ + +A new warning, C<!=~ should be !~>, is emitted to prevent this misspelling +of the non-matching operator. + +=item Newline in left-justified string + +The warning I<Newline in left-justified string> has been removed. + +=item Too late for "-T" option + +The error I<Too late for "-T" option> has been reformulated to be more +descriptive. + +=item "%s" variable %s masks earlier declaration + +This warning is now emitted in more consistent cases; in short, when one +of the declarations involved is a C<my> variable: + + my $x; my $x; # warns + my $x; our $x; # warns + our $x; my $x; # warns + +On the other hand, the following: + + our $x; our $x; + +now gives a C<"our" variable %s redeclared> warning. + +=item readdir()/closedir()/etc. attempted on invalid dirhandle + +These new warnings are now emitted when a dirhandle is used but is +either closed or not really a dirhandle. + +=item Opening dirhandle/filehandle %s also as a file/directory + +Two deprecation warnings have been added: (Rafael) + + Opening dirhandle %s also as a file + Opening filehandle %s also as a directory + +=item Use of -P is deprecated + +Perl's command-line switch C<-P> is now deprecated. + +=item v-string in use/require is non-portable + +Perl will warn you against potential backwards compatibility problems with +the C<use VERSION> syntax. + +=item perl -V + +C<perl -V> has several improvements, making it more useable from shell +scripts to get the value of configuration variables. See L<perlrun> for +details. + +=back + +=head1 Changed Internals + +In general, the source code of perl has been refactored, tidied up, +and optimized in many places. Also, memory management and allocation +has been improved in several points. + +When compiling the perl core with gcc, as many gcc warning flags are +turned on as is possible on the platform. (This quest for cleanliness +doesn't extend to XS code because we cannot guarantee the tidiness of +code we didn't write.) Similar strictness flags have been added or +tightened for various other C compilers. + +=head2 Reordering of SVt_* constants + +The relative ordering of constants that define the various types of C<SV> +have changed; in particular, C<SVt_PVGV> has been moved before C<SVt_PVLV>, +C<SVt_PVAV>, C<SVt_PVHV> and C<SVt_PVCV>. This is unlikely to make any +difference unless you have code that explicitly makes assumptions about that +ordering. (The inheritance hierarchy of C<B::*> objects has been changed +to reflect this.) + +=head2 Elimination of SVt_PVBM + +Related to this, the internal type C<SVt_PVBM> has been removed. This +dedicated type of C<SV> was used by the C<index> operator and parts of the +regexp engine to facilitate fast Boyer-Moore matches. Its use internally has +been replaced by C<SV>s of type C<SVt_PVGV>. + +=head2 New type SVt_BIND + +A new type C<SVt_BIND> has been added, in readiness for the project to +implement Perl 6 on 5. There deliberately is no implementation yet, and +they cannot yet be created or destroyed. + +=head2 Removal of CPP symbols + +The C preprocessor symbols C<PERL_PM_APIVERSION> and +C<PERL_XS_APIVERSION>, which were supposed to give the version number of +the oldest perl binary-compatible (resp. source-compatible) with the +present one, were not used, and sometimes had misleading values. They have +been removed. + +=head2 Less space is used by ops + +The C<BASEOP> structure now uses less space. The C<op_seq> field has been +removed and replaced by a single bit bit-field C<op_opt>. C<op_type> is now 9 +bits long. (Consequently, the C<B::OP> class doesn't provide an C<seq> +method anymore.) + +=head2 New parser + +perl's parser is now generated by bison (it used to be generated by +byacc.) As a result, it seems to be a bit more robust. + +Also, Dave Mitchell improved the lexer debugging output under C<-DT>. + +=head2 Use of C<const> + +Andy Lester supplied many improvements to determine which function +parameters and local variables could actually be declared C<const> to the C +compiler. Steve Peters provided new C<*_set> macros and reworked the core to +use these rather than assigning to macros in LVALUE context. + +=head2 Mathoms + +A new file, F<mathoms.c>, has been added. It contains functions that are +no longer used in the perl core, but that remain available for binary or +source compatibility reasons. However, those functions will not be +compiled in if you add C<-DNO_MATHOMS> in the compiler flags. + +=head2 C<AvFLAGS> has been removed + +The C<AvFLAGS> macro has been removed. + +=head2 C<av_*> changes + +The C<av_*()> functions, used to manipulate arrays, no longer accept null +C<AV*> parameters. + +=head2 $^H and %^H + +The implementation of the special variables $^H and %^H has changed, to +allow implementing lexical pragmas in pure Perl. + +=head2 B:: modules inheritance changed + +The inheritance hierarchy of C<B::> modules has changed; C<B::NV> now +inherits from C<B::SV> (it used to inherit from C<B::IV>). + +=head2 Anonymous hash and array constructors + +The anonymous hash and array constructors now take 1 op in the optree +instead of 3, now that pp_anonhash and pp_anonlist return a reference to +an hash/array when the op is flagged with OPf_SPECIAL. (Nicholas Clark) + +=head1 Known Problems + +There's still a remaining problem in the implementation of the lexical +C<$_>: it doesn't work inside C</(?{...})/> blocks. (See the TODO test in +F<t/op/mydef.t>.) + +Stacked filetest operators won't work when the C<filetest> pragma is in +effect, because they rely on the stat() buffer C<_> being populated, and +filetest bypasses stat(). + +=head2 UTF-8 problems + +The handling of Unicode still is unclean in several places, where it's +dependent on whether a string is internally flagged as UTF-8. This will +be made more consistent in perl 5.12, but that won't be possible without +a certain amount of backwards incompatibility. + +=head1 Platform Specific Problems + +When compiled with g++ and thread support on Linux, it's reported that the +C<$!> stops working correctly. This is related to the fact that the glibc +provides two strerror_r(3) implementation, and perl selects the wrong +one. + +=head1 Reporting Bugs + +If you find what you think is a bug, you might check the articles +recently posted to the comp.lang.perl.misc newsgroup and the perl +bug database at http://rt.perl.org/rt3/ . There may also be +information at http://www.perl.org/ , the Perl Home Page. + +If you believe you have an unreported bug, please run the B<perlbug> +program included with your release. Be sure to trim your bug down +to a tiny but sufficient test case. Your bug report, along with the +output of C<perl -V>, will be sent off to perlbug@perl.org to be +analysed by the Perl porting team. + +=head1 SEE ALSO + +The F<Changes> file and the perl590delta to perl595delta man pages for +exhaustive details on what changed. + +The F<INSTALL> file for how to build Perl. + +The F<README> file for general stuff. + +The F<Artistic> and F<Copying> files for copyright information. + +=cut |