perl593delta - what is new for perl v5.9.3
This document describes differences between the 5.9.2 and the 5.9.3 development releases. See perl590delta, perl591delta and perl592delta for the differences between 5.8.0 and 5.9.2.
-f _
The identifier _
is now forced to be a bareword after a filetest
operator. This solves a number of misparsing issues when a global _
subroutine is defined.
mkdir()mkdir() without arguments now defaults to $_
.
The construct eval { goto &foo }
is now disallowed. (Note that the
similar construct, but with eval("") instead, was already forbidden.)
$#
has been removedThe deprecated $#
variable (output format for numbers) has been
removed. A new warning, $# is no longer supported, has been added.
:unique
The :unique
attribute has been made a no-op, since its current
implementation was fundamentally flawed and not threadsafe.
sort pragmaThe sort pragma is now lexically scoped. Its effect used to be global.
feature
pragmaThe feature
pragma is used to enable new syntax that would break Perl's
backwards-compatibility with older releases of the language. It's a lexical
pragma, like strict
or warnings
.
Currently the following new features are available: switch
(adds a
switch statement), ~~
(adds a Perl 6-like smart match operator), say
(adds a say built-in function), and err
(adds an err
keyword).
Those features are described below.
Note that err
low-precedence defined-or operator used to be enabled by
default (although as a weak keyword, meaning that any function would
override it). It's now only recognized when explicitly turned on (and is
then a regular keyword).
Those features, and the feature
pragma itself, have been contributed by
Robin Houston.
Perl 5 now has a switch statement. It's available when use feature
'switch'
is in effect. This feature introduces three new keywords,
given
, when
, and default
:
- given ($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 when
conditions is given in Switch statements in perlsyn.
This kind of match is called smart match, and it's also possible to use
it outside of switch statements, via the new ~~
operator (enabled via
the use feature '~~'
directive). See Smart matching in detail in perlsyn.
say()say() is a new built-in, only available when use feature 'say'
is in
effect, that is similar to print(), but that implicitly appends a newline
to the printed string. See say.
CLONE_SKIP()
Perl has now support for the CLONE_SKIP
special subroutine. Like
CLONE
, CLONE_SKIP
is called once per package; however, it is called
just before cloning starts, and in the context of the parent thread. If it
returns a true value, then no objects of that class will be cloned. See
perlmod for details. (Contributed by Dave Mitchell.)
${^CHILD_ERROR_NATIVE}
A new internal variable, ${^CHILD_ERROR_NATIVE}
, gives the native
status returned by the last pipe close, backtick command, successful call
to wait() or waitpid(), or from the system() operator. See perlrun for
details. (Contributed by Gisle Aas.)
The support for assertions, introduced in perl 5.9.0, has been improved.
The syntax for the -A
command-line switch has changed; it now accepts
an optional module name, defaulting to assertions::activate
. See
assertions and perlrun. (Contributed by Salvador Fandiño García.)
The copy of the Unicode Character Database included in Perl 5.9 has been updated to 4.1.0.
no VERSION
You can now use no followed by a version number to specify that you
want to use a version of perl older than the specified one.
You can now use recursive subroutines with sort(), thanks to Robin Houston.
The compile-time value of the %^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("").
-E is equivalent to -e, but it implicitly enables all
optional features (like use feature ":5.10"
).
chdir, chmod and chown on filehandleschdir, chmod and chown can now work on filehandles as well as
filenames, if the system supports respectively fchdir
, fchmod
and
fchown
, thanks to a patch provided by Gisle Aas.
$(
and $)
now return groups in the order where the OS returns them,
thanks to Gisle Aas. This wasn't previously the case.
A new pragma, feature
, has been added; see above in Core Enhancements.
assertions::compat
, also available on CPAN, allows the use of assertions on
perl versions prior to 5.9.0 (that is the first one to natively support
them).
Math::BigInt::FastCalc
is an XS-enabled, and thus faster, version of
Math::BigInt::Calc
.
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 Archive::Tar
(see below).
IO::Zlib
is an IO::
-style interface to Compress::Zlib
.
Archive::Tar
is a module to manipulate tar
archives.
Digest::SHA
is a module used to calculate many types of SHA digests,
has been included for SHA support in the CPAN module.
ExtUtils::CBuilder
and ExtUtils::ParseXS
have been added.
ptar
ptar
is a pure perl implementation of tar
, that comes with
Archive::Tar
.
ptardiff
ptardiff
is a small script used to generate a diff between the contents
of a tar archive and a directory tree. Like ptar
, it comes with
Archive::Tar
.
shasum
This command-line utility, used to print or to check SHA digests, comes
with the new Digest::SHA
module.
h2xs
enhancementsh2xs
implements a new option --use-xsloader
to force use of
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.
perlivp
enhancementsperlivp
no longer checks for *.ph files by default. Use the new -a
option to run all tests.
The perlglossary manpage is a glossary of terms used in the Perl documentation, technical and otherwise, kindly provided by O'Reilly Media, Inc.
perltodo now lists a rough roadmap to Perl 5.10.
Some pure-perl code that perl was using to retrieve Unicode properties and transliteration mappings has been reimplemented in XS.
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 use POSIX;
now takes about
200K less memory.
PERL_DONT_CREATE_GVSV
The new compilation flag 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 perl589delta
for details.
Weak reference creation is now O(1) rather than O(n), courtesy of Nicholas Clark. Weak reference deletion remains O(n), but if deletion only happens at program exit, it may be skipped completely.
Salvador Fandiño provided improvements to reduce the memory usage of sort
and to speed up some cases.
Parallel makes should work properly now, although there may still be problems
if make test
is instructed to run in parallel.
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.
Perl extensions on Windows now can be statically built into the Perl DLL, thanks to a work by Vadim Konovalov.
Perl is being ported to Symbian OS. See perlsymbian for more information.
The VMS port has been improved. See perlvms.
DynaLoader::dl_unload_file() now works on Windows.
Portability of Perl on various recent compilers on Windows has been improved (Borland C++, Visual C++ 7.0).
Configure
will now detect clearenv
and unsetenv
, thanks to a
patch from Alan Burlison. It will also probe for futimes
(and use it
internally if available), and whether sprintf correctly returns the
length of the formatted string.
README files and changelogs for CPAN modules bundled with perl are no longer installed.
defined $$x
use strict "refs"
was ignoring taking a hard reference in an argument
to defined(), as in :
This now correctly produces the run-time error Can't use string as a
SCALAR ref while "strict refs" in use. (However, defined @$foo
and
defined %$foo
are still allowed. Those constructs are discouraged
anyway.)
CORE::require() and CORE::do() were always parsed as require() and do() when they were overridden. This is now fixed.
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 ->
was required.
Perl 5.9.2 introduced a change so that assignments of undef to a
scalar, or of an empty list to an array or a hash, were optimised out. As
this could cause problems when goto jumps were involved, this change
was backed out.
Using the sprintf() function with some formats could lead to a buffer overflow in some specific cases. This has been fixed, along with several other bugs, notably in bounds checking.
In related fixes, it was possible for badly written code that did not follow
the documentation of Sys::Syslog
to have formatting vulnerabilities.
Sys::Syslog
has been changed to protect people from poor quality third
party code.
Previously when running with warnings enabled globally via -w
, selective
disabling of specific warning categories would actually turn off all warnings.
This is now fixed; now no warnings 'io';
will only turn off warnings in the
io
class. Previously it would erroneously turn off all warnings.
FindBin
now works better with directories where access rights are more
restrictive than usual.
Several memory leaks in ithreads were closed. Also, ithreads were made less memory-intensive.
Trailing spaces are now trimmed from $!
and $^E
.
Operations that require perl to read a process's list of groups, such as reads
of $(
and $)
, now dynamically allocate memory rather than using a
fixed sized array. The fixed size array could cause C stack exhaustion on
systems configured to use large numbers of groups.
PerlIO::scalar
now works better with non-default $/
settings.
The x
repetition operator is now able to operate on qw// lists. This
used to raise a syntax error.
The debugger now traces correctly execution in eval("")uated code that contains #line directives.
The value of the open pragma is no longer ignored for three-argument
opens.
Perl will now use the C library calls unsetenv
and clearenv
if present
to delete keys from %ENV
and delete %ENV
entirely, thanks to a patch
from Alan Burlison.
chr() on a negative value now gives \x{FFFD}
, the Unicode replacement
character, unless when the bytes
pragma is in effect, where the low
eight bytes of the value are used.
Some case insensitive matches between UTF-8 encoded data and 8 bit regexps, and vice versa, could give malformed character warnings. These have been fixed by Dave Mitchell and Yves Orton.
lcfirst and ucfirst could corrupt the string for certain cases where
the length UTF-8 encoding of the string in lower case, upper case or title
case differed. This was fixed by Nicholas Clark.
This is a new warning, produced in situations like the following one:
This is a new warning, produced when number has been passed as a argument to select(), instead of a bitmask.
This syntax error indicates that the lexer couldn't find the final
delimiter of a ?PATTERN?
construct. Mentioning the ternary operator in
this error message makes syntax diagnostic easier.
This warning is now emitted in more consistent cases; in short, when one
of the declarations involved is a my variable:
On the other hand, the following:
now gives a "our" variable %s redeclared warning.
These new warnings are now emitted when a dirhandle is used but is either closed or not really a dirhandle.
In general, the source code of perl has been refactored, tied up, and optimized in many places. Also, memory management and allocation has been improved in a couple of points.
Andy Lester supplied many improvements to determine which function
parameters and local variables could actually be declared const
to the C
compiler. Steve Peters provided new *_set
macros and reworked the core to
use these rather than assigning to macros in LVALUE context.
Dave Mitchell improved the lexer debugging output under -DT
.
A new file, 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 -DNO_MATHOMS
in the compiler flags.
The AvFLAGS
macro has been removed.
The av_*()
functions, used to manipulate arrays, no longer accept null
AV*
parameters.
The inheritance hierarchy of B::
modules has changed; B::NV
now
inherits from B::SV
(it used to inherit from B::IV
).
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://bugs.perl.org/ . 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.
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.