perl593delta
(1)
Name
perl593delta - what is new for perl v5.9.3
Synopsis
Please see following description for synopsis
Description
Perl Programmers Reference Guide PERL593DELTA(1)
NAME
perl593delta - what is new for perl v5.9.3
DESCRIPTION
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.
Incompatible Changes
Parsing of "-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 $_.
Magic goto and eval
The construct "eval { goto &foo }" is now disallowed. (Note
that the similar construct, but with "eval("")" instead, was
already forbidden.)
$# has been removed
The 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.
Scoping of the "sort" pragma
The "sort" pragma is now lexically scoped. Its effect used
to be global.
Core Enhancements
The "feature" pragma
The "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
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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.
Switch and Smart Match operator
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 { $nothing = 1; }
}
A more complete description of how Perl matches the switch
variable against the "when" conditions is given in "Switch
statements" in perlsyn.
This kind of match is called smart match, and it's also
possible to use it outside of switch statements, via the new
"~~" operator (enabled via the "use feature '~~'"
directive). See "Smart matching in detail" in perlsyn.
"say()"
say() is a new built-in, only available when "use feature
'say'" is in effect, that is similar to print(), but that
implicitly appends a newline to the printed string. See
"say" in perlfunc.
"CLONE_SKIP()"
Perl has now support for the "CLONE_SKIP" special
subroutine. Like "CLONE", "CLONE_SKIP" is called once per
package; however, it is called just before cloning starts,
and in the context of the parent thread. If it returns a
true value, then no objects of that class will be cloned.
See perlmod for details. (Contributed by Dave Mitchell.)
"${^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.)
Assertions
The support for assertions, introduced in perl 5.9.0, has
been improved. The syntax for the "-A" command-line switch
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has changed; it now accepts an optional module name,
defaulting to "assertions::activate". See assertions and
perlrun. (Contributed by Salvador FandiA~Xo GarcA~a.)
Unicode Character Database 4.1.0
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.
Recursive sort subs
You can now use recursive subroutines with sort(), thanks to
Robin Houston.
Effect of pragmas in eval
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("").
New -E command-line switch
-E is equivalent to -e, but it implicitly enables all
optional features (like "use feature ":5.10"").
"chdir", "chmod" and "chown" on filehandles
"chdir", "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.
OS groups
$( and $) now return groups in the order where the OS
returns them, thanks to Gisle Aas. This wasn't previously
the case.
Modules and Pragmata
New Core Modules
o A new pragma, "feature", has been added; see above in
"Core Enhancements".
o "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).
o "Math::BigInt::FastCalc" is an XS-enabled, and thus
faster, version of "Math::BigInt::Calc".
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o "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).
o "IO::Zlib" is an "IO::"-style interface to
"Compress::Zlib".
o "Archive::Tar" is a module to manipulate "tar" archives.
o "Digest::SHA" is a module used to calculate many types
of SHA digests, has been included for SHA support in the
CPAN module.
o "ExtUtils::CBuilder" and "ExtUtils::ParseXS" have been
added.
Utility Changes
"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" enhancements
"h2xs" 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" enhancements
"perlivp" no longer checks for *.ph files by default. Use
the new "-a" option to run all tests.
Documentation
Perl Glossary
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.
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Performance Enhancements
XS-assisted SWASHGET
Some pure-perl code that perl was using to retrieve Unicode
properties and transliteration mappings has been
reimplemented in XS.
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
"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 references are cheaper
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.
sort() enhancements
Salvador FandiA~Xo provided improvements to reduce the
memory usage of "sort" and to speed up some cases.
Installation and Configuration Improvements
Compilation improvements
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.
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New Or Improved Platforms
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).
New probes
"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.
Module auxiliary files
README files and changelogs for CPAN modules bundled with
perl are no longer installed.
Selected Bug Fixes
"defined $$x"
"use strict "refs"" was ignoring taking a hard reference in
an argument to defined(), as in :
use strict "refs";
my $x = "foo";
if (defined $$x) {...}
This now correctly produces the run-time error "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.)
Calling CORE::require()
CORE::require() and CORE::do() were always parsed as
require() and do() when they were overridden. This is now
fixed.
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 "->" was required.
Remove over-optimisation
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
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hash, were optimised out. As this could cause problems when
"goto" jumps were involved, this change was backed out.
sprintf() fixes
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.
no warnings 'category' works correctly with -w
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.
Smaller fixes
o "FindBin" now works better with directories where access
rights are more restrictive than usual.
o Several memory leaks in ithreads were closed. Also,
ithreads were made less memory-intensive.
o Trailing spaces are now trimmed from $! and $^E.
o 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.
o "PerlIO::scalar" now works better with non-default $/
settings.
o The "x" repetition operator is now able to operate on
"qw//" lists. This used to raise a syntax error.
o The debugger now traces correctly execution in
eval("")uated code that contains #line directives.
o The value of the "open" pragma is no longer ignored for
three-argument opens.
o Perl will now use the C library calls "unsetenv" and
"clearenv" if present to delete keys from %ENV and
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delete %ENV entirely, thanks to a patch from Alan
Burlison.
More Unicode Fixes
o 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.
o 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.
o "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.
New or Changed Diagnostics
Attempt to set length of freed array
This is a new warning, produced in situations like the
following one:
$r = do {my @a; \$#a};
$$r = 503;
Non-string passed as bitmask
This is a new warning, produced when number has been passed
as a argument to select(), instead of a bitmask.
# Wrong, will now warn
$rin = fileno(STDIN);
($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);
# Should be
$rin = '';
vec($rin,fileno(STDIN),1) = 1;
($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);
Search pattern not terminated or ternary operator parsed as
search pattern
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.
"%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 "my"
variable:
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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 ""our" variable %s redeclared" warning.
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.
Changed Internals
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.
B:: modules inheritance changed
The inheritance hierarchy of "B::" modules has changed;
"B::NV" now inherits from "B::SV" (it used to inherit from
"B::IV").
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://bugs.perl.org/
. There may also be information at http://www.perl.org/ ,
the Perl Home Page.
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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 [email protected] to be analysed by the Perl porting team.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/perl-512 |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
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.
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://www.cpan.org/src/5.0/perl-5.12.5.tar.bz2
Further information about this software can be found on the
open source community website at http://www.perl.org/.
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