NAME
perl595delta - what is new for perl v5.9.5
DESCRIPTION
This document describes differences between the 5.9.4 and the 5.9.5
development releases. See perl590delta, perl591delta, perl592delta,
perl593delta and perl594delta for the differences between 5.8.0 and
5.9.4.
Incompatible Changes
Tainting and printf
When perl is run under taint mode, "printf()" and "sprintf()" will now
reject any tainted format argument. (Rafael Garcia-Suarez)
undef and signal handlers
Undefining or deleting a signal handler via "undef $SIG{FOO}" is now
equivalent to setting it to 'DEFAULT'. (Rafael)
strictures and array/hash dereferencing in defined()
"defined @$foo" and "defined %$bar" are now subject to "strict 'refs'"
(that is, $foo and $bar shall be proper references there.) (Nicholas
Clark)
(However, "defined(@foo)" and "defined(%bar)" are discouraged
constructs anyway.)
"(?p{})" has been removed
The regular expression construct "(?p{})", which was deprecated in perl
5.8, has been removed. Use "(??{})" instead. (Rafael)
Pseudo-hashes have been removed
Support for pseudo-hashes has been removed from Perl 5.9. (The "fields"
pragma remains here, but uses an alternate implementation.)
Removal of the bytecode compiler and of perlcc
"perlcc", the byteloader and the supporting modules (B::C, B::CC,
B::Bytecode, etc.) are no longer distributed with the perl sources.
Those experimental tools have never worked reliably, and, due to the
lack of volunteers to keep them in line with the perl interpreter
developments, it was decided to remove them instead of shipping a
broken version of those. The last version of those modules can be
found with perl 5.9.4.
However the B compiler framework stays supported in the perl core, as
with the more useful modules it has permitted (among others, B::Deparse
and B::Concise).
Removal of the JPL
The JPL (Java-Perl Linguo) has been removed from the perl sources
tarball.
Recursive inheritance detected earlier
Perl will now immediately throw an exception if you modify any
package’s @ISA in such a way that it would cause recursive inheritance.
Previously, the exception would not occur until Perl attempted to make
use of the recursive inheritance while resolving a method or doing a
"$foo->isa($bar)" lookup.
Core Enhancements
Regular expressions
Recursive Patterns
It is now possible to write recursive patterns without using the
"(??{})" 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 "(?PARNO)" syntax ("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
Note, users experienced with PCRE will find that the Perl
implementation of this feature differs from the PCRE one in that it
is possible to backtrack into a recursed pattern, whereas in PCRE
the recursion is atomic or "possessive" in nature. (Yves Orton)
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
"(?<NAME>....)". It’s possible to backreference to a named buffer
with the "\k<NAME>" syntax. In code, the new magical hashes "%+"
and "%-" can be used to access the contents of the capture buffers.
Thus, to replace all doubled chars, one could write
s/(?<letter>.)\k<letter>/$+{letter}/g
Only buffers with defined contents will be "visible" in the "%+"
hash, so it’s possible to do something like
foreach my $name (keys %+) {
print "content of buffer '$name' is $+{$name}\n";
}
The "%-" 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.
"%+" and "%-" are implemented as tied hashes through the new module
"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)
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 "?+",
"*+", "++", "{min,max}+" are now legal quantifiers. (Yves Orton)
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 perlre for their descriptions. (Yves
Orton)
Relative backreferences
A new syntax "\g{N}" or "\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 "Capture buffers"
in perlre. (Yves Orton)
"\K" escape
The functionality of Jeff Pinyan’s module Regexp::Keep has been
added to the core. You can now use in regular expressions the
special escape "\K" as a way to do something like floating length
positive lookbehind. It is also useful in substitutions like:
s/(foo)bar/$1/g
that can now be converted to
s/foo\Kbar//g
which is much more efficient. (Yves Orton)
Vertical and horizontal whitespace, and linebreak
Regular expressions now recognize the "\v" and "\h" escapes, that
match vertical and horizontal whitespace, respectively. "\V" and
"\H" logically match their complements.
"\R" matches a generic linebreak, that is, vertical whitespace,
plus the multi-character sequence "\x0D\x0A".
The "_" prototype
A new prototype character has been added. "_" is equivalent to "$" (it
denotes a scalar), but defaults to $_ if the corresponding argument
isn’t supplied. 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 "_" for some built-ins in appropriate cases
(for example, "prototype('CORE::rmdir')"). (Rafael)
UNITCHECK blocks
"UNITCHECK", a new special code block has been introduced, in addition
to "BEGIN", "CHECK", "INIT" and "END".
"CHECK" and "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, "UNITCHECK" blocks are executed
just after the unit which defined them has been compiled. See perlmod
for more information. (Alex Gough)
readpipe() is now overridable
The built-in function readpipe() is now overridable. Overriding it
permits also to override its operator counterpart, "qx//" (a.k.a.
"``"). Moreover, it now defaults to $_ if no argument is provided.
(Rafael)
default argument for readline()
readline() now defaults to *ARGV if no argument is provided. (Rafael)
UCD 5.0.0
The copy of the Unicode Character Database included in Perl 5.9 has
been updated to version 5.0.0.
Smart match
The smart match operator ("~~") is now available by default (you don’t
need to enable it with "use feature" any longer). (Michael G Schwern)
Implicit loading of "feature"
The "feature" pragma is now implicitly loaded when you require a
minimal perl version (with the "use VERSION" construct) greater than,
or equal to, 5.9.5.
Modules and Pragmas
New Pragma, "mro"
A new pragma, "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 mro for more information.
(Brandon Black)
Note that, due to changes in the implementation of class hierarchy
search, code that used to undef the *ISA glob will most probably break.
Anyway, undef’ing *ISA had the side-effect of removing the magic on the
@ISA array and should not have been done in the first place.
bignum, bigint, bigrat
The three numeric pragmas "bignum", "bigint" and "bigrat" are now
lexically scoped. (Tels)
Math::BigInt/Math::BigFloat
Many bugs have been fixed; noteworthy are comparisons with NaN, which
no longer warn about undef values.
The following things are new:
config()
The config() method now also supports the calling-style
"config('lib')" in addition to "config()->{'lib'}".
import()
Upon import, using "lib => 'Foo'" now warns if the low-level
library cannot be found. To suppress the warning, you can use "try
=> 'Foo'" instead. To convert the warning into a die, use "only =>
'Foo'" instead.
roundmode common
A rounding mode of "common" is now supported.
Also, support for the following methods has been added:
bpi(), bcos(), bsin(), batan(), batan2()
bmuladd()
bexp(), bnok()
from_hex(), from_oct(), and from_bin()
as_oct()
In addition, the default math-backend (Calc (Perl) and FastCalc (XS))
now support storing numbers in parts with 9 digits instead of 7 on
Perls with either 64bit integer or long double support. This means math
operations scale better and are thus faster for really big numbers.
New Core Modules
· "Locale::Maketext::Simple", needed by CPANPLUS, is a simple wrapper
around "Locale::Maketext::Lexicon". Note that
"Locale::Maketext::Lexicon" isn’t included in the perl core; the
behaviour of "Locale::Maketext::Simple" gracefully degrades when
the later isn’t present.
· "Params::Check" implements a generic input parsing/checking
mechanism. It is used by CPANPLUS.
· "Term::UI" simplifies the task to ask questions at a terminal
prompt.
· "Object::Accessor" provides an interface to create per-object
accessors.
· "Module::Pluggable" is a simple framework to create modules that
accept pluggable sub-modules.
· "Module::Load::Conditional" provides simple ways to query and
possibly load installed modules.
· "Time::Piece" provides an object oriented interface to time
functions, overriding the built-ins localtime() and gmtime().
· "IPC::Cmd" helps to find and run external commands, possibly
interactively.
· "File::Fetch" provide a simple generic file fetching mechanism.
· "Log::Message" and "Log::Message::Simple" are used by the log
facility of "CPANPLUS".
· "Archive::Extract" is a generic archive extraction mechanism for
.tar (plain, gziped or bzipped) or .zip files.
· "CPANPLUS" provides an API and a command-line tool to access the
CPAN mirrors.
Module changes
"assertions"
The "assertions" pragma, its submodules "assertions::activate" and
"assertions::compat" and the -A command-line switch have been
removed. The interface was not judged mature enough for inclusion
in a stable release.
"base"
The "base" pragma now warns if a class tries to inherit from
itself. (Curtis "Ovid" Poe)
"strict" and "warnings"
"strict" and "warnings" will now complain loudly if they are loaded
via incorrect casing (as in "use Strict;"). (Johan Vromans)
"warnings"
The "warnings" pragma doesn’t load "Carp" anymore. That means that
code that used "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";
"less"
"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
less for more. (Joshua ben Jore)
"Attribute::Handlers"
"Attribute::Handlers" can now report the caller’s file and line
number. (David Feldman)
"B::Lint"
"B::Lint" is now based on "Module::Pluggable", and so can be
extended with plugins. (Joshua ben Jore)
"B" It’s now possible to access the lexical pragma hints ("%^H") by
using the method B::COP::hints_hash(). It returns a "B::RHE"
object, which in turn can be used to get a hash reference via the
method B::RHE::HASH(). (Joshua ben Jore)
"Thread"
As the old 5005thread threading model has been removed, in favor of
the ithreads scheme, the "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.
Utility Changes
"cpanp"
"cpanp", the CPANPLUS shell, has been added. ("cpanp-run-perl", an
helper for CPANPLUS operation, has been added too, but isn’t intended
for direct use).
"cpan2dist"
"cpan2dist" is a new utility, that comes with CPANPLUS. It’s a tool to
create distributions (or packages) from CPAN modules.
"pod2html"
The output of "pod2html" has been enhanced to be more customizable via
CSS. Some formatting problems were also corrected. (Jari Aalto)
Documentation
New manpage, perlunifaq
A new manual page, perlunifaq (the Perl Unicode FAQ), has been added
(Juerd Waalboer).
Installation and Configuration Improvements
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.)
Visual C++
Perl now can be compiled with Microsoft Visual C++ 2005.
Static build on Win32
It’s now possible to build a "perl-static.exe" that doesn’t depend on
"perl59.dll" on Win32. See the Win32 makefiles for details. (Vadim
Konovalov)
win32 builds
All win32 builds (MS-Win, WinCE) have been merged and cleaned up.
"d_pseudofork" and "d_printf_format_null"
A new configuration variable, available as $Config{d_pseudofork} in the
Config module, has been added, to distinguish real fork() support from
fake pseudofork used on Windows platforms.
A new configuration variable, "d_printf_format_null", has been added,
to see if printf-like formats are allowed to be NULL.
Help
"Configure -h" has been extended with the most used option.
Much less ’Whoa there’ messages.
64bit systems
Better detection of 64bit(only) systems, and setting all the (library)
paths accordingly.
Ports
Perl has been reported to work on MidnightBSD.
Support for Cray XT4 Catamount/Qk has been added.
Vendor patches have been merged for RedHat and GenToo.
Selected Bug Fixes
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)
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)
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 "Deferred
Signals (Safe Signals)" in perlipc). (Rafael)
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)
The "-w" and "-t" switches can now be used together without messing up
what categories of warnings are activated or not. (Rafael)
Duping a filehandle which has the ":utf8" PerlIO layer set will now
properly carry that layer on the duped filehandle. (Rafael)
Localizing an 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 "local $h{$x}; ++$x"). (Bo Lindbergh)
New or Changed Diagnostics
Deprecations
Two deprecation warnings have been added: (Rafael)
Opening dirhandle %s also as a file
Opening filehandle %s also as a directory
Changed Internals
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).
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 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 "perl -V", will be sent off to perlbug@perl.org to be analysed by
the Perl porting team.
SEE ALSO
The Changes file for exhaustive details on what changed.
The INSTALL file for how to build Perl.
The README file for general stuff.
The Artistic and Copying files for copyright information.