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NAME

perl5005delta - what's new for perl5.005
 

DESCRIPTION

About the new versioning system

Perl 5.005 is the combined product of the new dual-track development scheme.  

Incompatible Changes

WARNING: This version is not binary compatible with Perl 5.004.

Default installation structure has changed

Perl Source Compatibility

If threads are enabled, then some caveats apply. @_ and $_ become lexical variables. The effect of this should be largely transparent to the user, but there are some boundary conditions under which user will need to be aware of the issues. For example, "local(@_)" results in a ``Can't localize lexical variable @_ ...'' message. This may be enabled in a future version.

Some new keywords have been introduced. These are generally expected to have very little impact on compatibility. See "New "INIT" keyword", "New "lock" keyword", and "New "qr//" operator".

Certain barewords are now reserved. Use of these will provoke a warning if you have asked for them with the "-w" switch. See ""our" is now a reserved word".  

C Source Compatibility

*

Core sources now require ANSI C compiler

An ANSI C compiler is now required to build perl. See INSTALL.

*

All Perl global variables must now be referenced with an explicit prefix

All Perl global variables that are visible for use by extensions now have a "PL_" prefix. New extensions should "not" refer to perl globals by their unqualified names. To preserve sanity, we provide limited backward compatibility for globals that are being widely used like "sv_undef" and "na" (which should now be written as "PL_sv_undef", "PL_na" etc.)

If you find that your XS extension does not compile anymore because a perl global is not visible, try adding a "PL_" prefix to the global and rebuild.

It is strongly recommended that all functions in the Perl API that don't begin with "perl" be referenced with a "Perl_" prefix. The bare function names without the "Perl_" prefix are supported with macros, but this support may cease in a future release.

See perlapi.

*

Enabling threads has source compatibility issues

Perl built with threading enabled requires extensions to use the new "dTHR" macro to initialize the handle to access per-thread data. If you see a compiler error that talks about the variable "thr" not being declared (when building a module that has XS code), you need to add "dTHR;" at the beginning of the block that elicited the error.

The API function "perl_get_sv("@",FALSE)" should be used instead of directly accessing perl globals as "GvSV(errgv)". The API call is backward compatible with existing perls and provides source compatibility with threading is enabled.

See ``C Source Compatibility'' for more information.

Binary Compatibility

Security fixes may affect compatibility

Oneliners with the "-e" switch do not create temporary files anymore.  

Relaxed new mandatory warnings introduced in 5.004

Licensing

The license included in much of the Perl documentation has changed. Most of the Perl documentation was previously under the implicit GNU General Public License or the Artistic License (at the user's choice). Now much of the documentation unambiguously states the terms under which it may be distributed. Those terms are in general much less restrictive than the GNU GPL. See perl and the individual perl manpages listed therein.  

Core Changes

Threads

See README.threads.  

Compiler

The Compiler produces three different types of transformations of a perl program. The C backend generates C code that captures perl's state just before execution begins. It eliminates the compile-time overheads of the regular perl interpreter, but the run-time performance remains comparatively the same. The CC backend generates optimized C code equivalent to the code path at run-time. The CC backend has greater potential for big optimizations, but only a few optimizations are implemented currently. The Bytecode backend generates a platform independent bytecode representation of the interpreter's state just before execution. Thus, the Bytecode back end also eliminates much of the compilation overhead of the interpreter.

The compiler comes with several valuable utilities.

"B::Lint" is an experimental module to detect and warn about suspicious code, especially the cases that the "-w" switch does not detect.

"B::Deparse" can be used to demystify perl code, and understand how perl optimizes certain constructs.

"B::Xref" generates cross reference reports of all definition and use of variables, subroutines and formats in a program.

"B::Showlex" show the lexical variables used by a subroutine or file at a glance.

"perlcc" is a simple frontend for compiling perl.

See "ext/B/README", B, and the respective compiler modules.  

Regular Expressions

Here is an itemized summary:

Many new and improved optimizations

Changes in the RE engine:

        Unneeded nodes removed;
        Substrings merged together;
        New types of nodes to process (SUBEXPR)* and similar expressions
            quickly, used if the SUBEXPR has no side effects and matches
            strings of the same length;
        Better optimizations by lookup for constant substrings;
        Better search for constants substrings anchored by $ ;

Changes in Perl code using RE engine:

        More optimizations to s/longer/short/;
        study() was not working;
        /blah/ may be optimized to an analogue of index() if $& $` $' not seen;
        Unneeded copying of matched-against string removed;
        Only matched part of the string is copying if $` $' were not seen;

Many bug fixes

Note that only the major bug fixes are listed here. See Changes for others.

        Backtracking might not restore start of $3.
        No feedback if max count for * or + on "complex" subexpression
            was reached, similarly (but at compile time) for {3,34567}
        Primitive restrictions on max count introduced to decrease a 
            possibility of a segfault;
        (ZERO-LENGTH)* could segfault;
        (ZERO-LENGTH)* was prohibited;
        Long REs were not allowed;
        /RE/g could skip matches at the same position after a 
          zero-length match;

New regular expression constructs

The following new syntax elements are supported:

        (?<=RE)
        (?<!RE)
        (?{ CODE })
        (?i-x)
        (?i:RE)
        (?(COND)YES_RE|NO_RE)
        (?>RE)
        \z

New operator for precompiled regular expressions

See "New "qr//" operator".

Other improvements

        Better debugging output (possibly with colors),
            even from non-debugging Perl;
        RE engine code now looks like C, not like assembler;
        Behaviour of RE modifiable by `use re' directive;
        Improved documentation;
        Test suite significantly extended;
        Syntax [:^upper:] etc., reserved inside character classes;

Incompatible changes

        (?i) localized inside enclosing group;
        $( is not interpolated into RE any more;
        /RE/g may match at the same position (with non-zero length)
            after a zero-length match (bug fix).

See perlre and perlop.  

Improved malloc()

Quicksort is internally implemented

See "perlfunc/sort".  

Reliable signals

However, one experimental implementation of reliable signals is available when threads are enabled. See "Thread::Signal". Also see INSTALL for how to build a Perl capable of threads.  

Reliable stack pointers

More generous treatment of carriage returns

Note that this doesn't somehow magically allow you to keep all text files in DOS format. The generous treatment only applies to files that perl itself parses. If your C compiler doesn't allow carriage returns in files, you may still be unable to build modules that need a C compiler.  

Memory leaks

Better support for multiple interpreters

Behavior of local() on array and hash elements is now well-defined

%! is transparently tied to the Errno module

Pseudo-hashes are supported

EXPR foreach EXPR is supported

Keywords can be globally overridden

$^E is meaningful on Win32

foreach (1..1000000) optimized

Foo:: can be used as implicitly quoted package name

exists $Foo::{Bar::} tests existence of a package

Better locale support

Experimental support for 64-bit platforms

prototype() returns useful results on builtins

Extended support for exception handling

Re-blessing in DESTROY() supported for chaining DESTROY() methods

All printf format conversions are handled internally

New INIT keyword

New lock keyword

To minimize impact on source compatibility this keyword is ``weak'', i.e., any user-defined subroutine of the same name overrides it, unless a "use Thread" has been seen.  

New qr// operator

our is now a reserved word

Tied arrays are now fully supported

Tied handles support is better

4th argument to substr

Negative LENGTH argument to splice

Magic lvalues are now more magical

    $x = "hello";
    sub printit {
        $x = "g'bye";
        print $_[0], "\n";
    }
    printit(substr($x, 0, 5));

In previous versions, this would print ``hello'', but it now prints ``g'bye''.  

<> now reads in records

Supported Platforms

New Platforms

DOS is now supported under the DJGPP tools. See README.dos (installed as perldos on some systems).

MiNT is now supported. See README.mint.

MPE/iX is now supported. See README.mpeix.

MVS (aka OS390, aka Open Edition) is now supported. See README.os390 (installed as perlos390 on some systems).

Stratus VOS is now supported. See README.vos.  

Changes in existing support

VMS configuration system has been rewritten. See README.vms (installed as README_vms on some systems).

The hints files for most Unix platforms have seen incremental improvements.  

Modules and Pragmata

New Modules

B

Perl compiler and tools. See B.

Data::Dumper

A module to pretty print Perl data. See Data::Dumper.

Dumpvalue

A module to dump perl values to the screen. See Dumpvalue.

Errno

A module to look up errors more conveniently. See Errno.

File::Spec

A portable API for file operations.

ExtUtils::Installed

Query and manage installed modules.

ExtUtils::Packlist

Manipulate .packlist files.

Fatal

Make functions/builtins succeed or die.

IPC::SysV

Constants and other support infrastructure for System V IPC operations in perl.

Test

A framework for writing testsuites.

Tie::Array

Base class for tied arrays.

Tie::Handle

Base class for tied handles.

Thread

Perl thread creation, manipulation, and support.

attrs

Set subroutine attributes.

fields

Compile-time class fields.

re

Various pragmata to control behavior of regular expressions.

Changes in existing modules

Benchmark

You can now run tests for x seconds instead of guessing the right number of tests to run.

Keeps better time.

Carp

Carp has a new function cluck(). cluck() warns, like carp(), but also adds a stack backtrace to the error message, like confess().

CGI

CGI has been updated to version 2.42.

Fcntl

More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for large (more than 4G) file access (the 64-bit support is not yet working, though, so no need to get overly excited), Free/Net/OpenBSD locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR.

Math::Complex

The accessors methods Re, Im, arg, abs, rho, theta, methods can ($z->Re()) now also act as mutators ($z->Re(3)).

Math::Trig

A little bit of radial trigonometry (cylindrical and spherical) added, for example the great circle distance.

POSIX

POSIX now has its own platform-specific hints files.

DB_File

DB_File supports version 2.x of Berkeley DB. See "ext/DB_File/Changes".

MakeMaker

MakeMaker now supports writing empty makefiles, provides a way to specify that site umask() policy should be honored. There is also better support for manipulation of .packlist files, and getting information about installed modules.

Extensions that have both architecture-dependent and architecture-independent files are now always installed completely in the architecture-dependent locations. Previously, the shareable parts were shared both across architectures and across perl versions and were therefore liable to be overwritten with newer versions that might have subtle incompatibilities.

CPAN

See perlmodinstall and CPAN.

Cwd

Cwd::cwd is faster on most platforms.

Utility Changes

"perlcc", a new experimental front end for the compiler is available.

The crude GNU "configure" emulator is now called "configure.gnu" to avoid trampling on "Configure" under case-insensitive filesystems.

"perldoc" used to be rather slow. The slower features are now optional. In particular, case-insensitive searches need the "-i" switch, and recursive searches need "-r". You can set these switches in the "PERLDOC" environment variable to get the old behavior.  

Documentation Changes

Porting/patching.pod has detailed instructions on how to create and submit patches for perl.

perlport specifies guidelines on how to write portably.

perlmodinstall describes how to fetch and install modules from "CPAN" sites.

Some more Perl traps are documented now. See perltrap.

perlopentut gives a tutorial on using open().

perlreftut gives a tutorial on references.

perlthrtut gives a tutorial on threads.  

New Diagnostics

Ambiguous call resolved as CORE::%s(), qualify as such or use &

(W) A subroutine you have declared has the same name as a Perl keyword, and you have used the name without qualification for calling one or the other. Perl decided to call the builtin because the subroutine is not imported.

To force interpretation as a subroutine call, either put an ampersand before the subroutine name, or qualify the name with its package. Alternatively, you can import the subroutine (or pretend that it's imported with the "use subs" pragma).

To silently interpret it as the Perl operator, use the "CORE::" prefix on the operator (e.g. "CORE::log($x)") or by declaring the subroutine to be an object method (see attrs).

Bad index while coercing array into hash

(F) The index looked up in the hash found as the 0'th element of a pseudo-hash is not legal. Index values must be at 1 or greater. See perlref.

Bareword %s refers to nonexistent package

(W) You used a qualified bareword of the form "Foo::", but the compiler saw no other uses of that namespace before that point. Perhaps you need to predeclare a package?

Can't call method %s on an undefined value

(F) You used the syntax of a method call, but the slot filled by the object reference or package name contains an undefined value. Something like this will reproduce the error:

    $BADREF = 42;
    process $BADREF 1,2,3;
    $BADREF->process(1,2,3);

Can't check filesystem of script %s for nosuid

(P) For some reason you can't check the filesystem of the script for nosuid.

Can't coerce array into hash

(F) You used an array where a hash was expected, but the array has no information on how to map from keys to array indices. You can do that only with arrays that have a hash reference at index 0.

Can't goto subroutine from an eval-string

(F) The ``goto subroutine'' call can't be used to jump out of an eval ``string''. (You can use it to jump out of an eval {BLOCK}, but you probably don't want to.)

Can't localize pseudo-hash element

(F) You said something like "local $ar->{'key'}", where $ar is a reference to a pseudo-hash. That hasn't been implemented yet, but you can get a similar effect by localizing the corresponding array element directly --- "local $ar->[$ar->[0]{'key'}]".

Can't use %%! because Errno.pm is not available

(F) The first time the %! hash is used, perl automatically loads the Errno.pm module. The Errno module is expected to tie the %! hash to provide symbolic names for $! errno values.

Cannot find an opnumber for %s

(F) A string of a form "CORE::word" was given to prototype(), but there is no builtin with the name "word".

Character class syntax [. .] is reserved for future extensions

(W) Within regular expression character classes ([]) the syntax beginning with ``[.'' and ending with ``.]'' is reserved for future extensions. If you need to represent those character sequences inside a regular expression character class, just quote the square brackets with the backslash: ``\[.'' and ``.\]''.

Character class syntax [: :] is reserved for future extensions

(W) Within regular expression character classes ([]) the syntax beginning with ``[:'' and ending with ``:]'' is reserved for future extensions. If you need to represent those character sequences inside a regular expression character class, just quote the square brackets with the backslash: ``\[:'' and ``:\]''.

Character class syntax [= =] is reserved for future extensions

(W) Within regular expression character classes ([]) the syntax beginning with ``[='' and ending with ``=]'' is reserved for future extensions. If you need to represent those character sequences inside a regular expression character class, just quote the square brackets with the backslash: ``\[='' and ``=\]''.

%s: Eval-group in insecure regular expression

(F) Perl detected tainted data when trying to compile a regular expression that contains the "(?{ ... })" zero-width assertion, which is unsafe. See ``(?{ code })'' in perlre, and perlsec.

%s: Eval-group not allowed, use re 'eval'

(F) A regular expression contained the "(?{ ... })" zero-width assertion, but that construct is only allowed when the "use re 'eval'" pragma is in effect. See ``(?{ code })'' in perlre.

%s: Eval-group not allowed at run time

(F) Perl tried to compile a regular expression containing the "(?{ ... })" zero-width assertion at run time, as it would when the pattern contains interpolated values. Since that is a security risk, it is not allowed. If you insist, you may still do this by explicitly building the pattern from an interpolated string at run time and using that in an eval(). See ``(?{ code })'' in perlre.

Explicit blessing to '' (assuming package main)

(W) You are blessing a reference to a zero length string. This has the effect of blessing the reference into the package main. This is usually not what you want. Consider providing a default target package, e.g. bless($ref, $p || 'MyPackage');

Illegal hex digit ignored

(W) You may have tried to use a character other than 0 - 9 or A - F in a hexadecimal number. Interpretation of the hexadecimal number stopped before the illegal character.

No such array field

(F) You tried to access an array as a hash, but the field name used is not defined. The hash at index 0 should map all valid field names to array indices for that to work.

No such field %s in variable %s of type %s

(F) You tried to access a field of a typed variable where the type does not know about the field name. The field names are looked up in the %FIELDS hash in the type package at compile time. The %FIELDS hash is usually set up with the 'fields' pragma.

Out of memory during ridiculously large request

(F) You can't allocate more than 2^31+``small amount'' bytes. This error is most likely to be caused by a typo in the Perl program. e.g., $arr[time] instead of $arr[$time].

Range iterator outside integer range

(F) One (or both) of the numeric arguments to the range operator ``..'' are outside the range which can be represented by integers internally. One possible workaround is to force Perl to use magical string increment by prepending ``0'' to your numbers.

Recursive inheritance detected while looking for method '%s' %s

(F) More than 100 levels of inheritance were encountered while invoking a method. Probably indicates an unintended loop in your inheritance hierarchy.

Reference found where even-sized list expected

(W) You gave a single reference where Perl was expecting a list with an even number of elements (for assignment to a hash). This usually means that you used the anon hash constructor when you meant to use parens. In any case, a hash requires key/value pairs.

    %hash = { one => 1, two => 2, };   # WRONG
    %hash = [ qw/ an anon array / ];   # WRONG
    %hash = ( one => 1, two => 2, );   # right
    %hash = qw( one 1 two 2 );                 # also fine

Undefined value assigned to typeglob

(W) An undefined value was assigned to a typeglob, a la "*foo = undef". This does nothing. It's possible that you really mean "undef *foo".

Use of reserved word %s is deprecated

(D) The indicated bareword is a reserved word. Future versions of perl may use it as a keyword, so you're better off either explicitly quoting the word in a manner appropriate for its context of use, or using a different name altogether. The warning can be suppressed for subroutine names by either adding a "&" prefix, or using a package qualifier, e.g. "&our()", or "Foo::our()".

perl: warning: Setting locale failed.

(S) The whole warning message will look something like:

       perl: warning: Setting locale failed.
       perl: warning: Please check that your locale settings:
               LC_ALL = "En_US",
               LANG = (unset)
           are supported and installed on your system.
       perl: warning: Falling back to the standard locale ("C").

Exactly what were the failed locale settings varies. In the above the settings were that the LC_ALL was ``En_US'' and the LANG had no value. This error means that Perl detected that you and/or your system administrator have set up the so-called variable system but Perl could not use those settings. This was not dead serious, fortunately: there is a ``default locale'' called ``C'' that Perl can and will use, the script will be run. Before you really fix the problem, however, you will get the same error message each time you run Perl. How to really fix the problem can be found in ``LOCALE PROBLEMS'' in perllocale.

Obsolete Diagnostics

Can't mktemp()

(F) The mktemp() routine failed for some reason while trying to process a -e switch. Maybe your /tmp partition is full, or clobbered.

Removed because -e doesn't use temporary files any more.

Can't write to temp file for -e: %s

(F) The write routine failed for some reason while trying to process a -e switch. Maybe your /tmp partition is full, or clobbered.

Removed because -e doesn't use temporary files any more.

Cannot open temporary file

(F) The create routine failed for some reason while trying to process a -e switch. Maybe your /tmp partition is full, or clobbered.

Removed because -e doesn't use temporary files any more.

regexp too big

(F) The current implementation of regular expressions uses shorts as address offsets within a string. Unfortunately this means that if the regular expression compiles to longer than 32767, it'll blow up. Usually when you want a regular expression this big, there is a better way to do it with multiple statements. See perlre.

Configuration Changes

BUGS

If you believe you have an unreported bug, please run the perlbug program included with your release. Make sure you 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.  

SEE ALSO

The INSTALL file for how to build Perl.

The README file for general stuff.

The Artistic and Copying files for copyright information.  

HISTORY

Send omissions or corrections to <[email protected]>.

Index

NAME

DESCRIPTION

About the new versioning system

Incompatible Changes

WARNING: This version is not binary compatible with Perl 5.004.

Default installation structure has changed

Perl Source Compatibility

C Source Compatibility

Binary Compatibility

Security fixes may affect compatibility

Relaxed new mandatory warnings introduced in 5.004

Licensing

Core Changes

Threads

Compiler

Regular Expressions

Improved malloc()

Quicksort is internally implemented

Reliable signals

Reliable stack pointers

More generous treatment of carriage returns

Memory leaks

Better support for multiple interpreters

Behavior of local() on array and hash elements is now well-defined

! is transparently tied to the Errno module

Pseudo-hashes are supported

EXPR foreach EXPR is supported

Keywords can be globally overridden

$^E is meaningful on Win32

foreach (1..1000000) optimized

Foo:: can be used as implicitly quoted package name

exists $Foo::{Bar::} tests existence of a package

Better locale support

Experimental support for 64-bit platforms

prototype() returns useful results on builtins

Extended support for exception handling

Re-blessing in DESTROY() supported for chaining DESTROY() methods

All printf format conversions are handled internally

New INIT keyword

New lock keyword

New qr// operator

our is now a reserved word

Tied arrays are now fully supported

Tied handles support is better

4th argument to substr

Negative LENGTH argument to splice

Magic lvalues are now more magical

<> now reads in records

Supported Platforms

New Platforms

Changes in existing support

Modules and Pragmata

New Modules

Changes in existing modules

Utility Changes

Documentation Changes

New Diagnostics

Obsolete Diagnostics

Configuration Changes

BUGS

SEE ALSO

HISTORY

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