perldelta - what's new for perl5.004


This document describes differences between the 5.003 release (as documented in Programming Perl, second edition--the Camel Book) and this one.

Supported Environments

Perl5.004 builds out of the box on Unix, Plan9, LynxOS, VMS, OS/2, QNX, and AmigaOS.

Core Changes

Most importantly, many bugs were fixed. See the Changes file in the distribution for details.

Compilation Option: Binary Compatibility With 5.003

There is a new Configure question that asks if you want to maintain binary compatibility with Perl 5.003. If you choose binary compatibility, you do not have to recompile your extensions, but you might have symbol conflicts if you embed Perl in another application, just as in the 5.003 release. By default, binary compatibility is preserved at the expense of symbol table pollution.

Subroutine Parameters Are Not Autovivified

In Perl versions 5.002 and 5.003, array and hash elements used as subroutine parameters were ``autovivified''; that is, they were brought into existence if they did not already exist. For example, calling func would create $h{foo} if it did not already exist, causing exists $h{foo} to become true and keys %h to return .

Perl 5.004 returns to the pre-5.002 behavior of not autovivifying array and hash elements used as subroutine parameters.

Fixed Parsing of $$, &$, etc.

A bug in previous versions of Perl 5.0 prevented proper parsing of numeric special variables as symbolic references. That bug has been fixed. As a result, the string ``$$0'' is no longer equivalent to $$."0", but rather to ${$0}. To get the old behavior, change ``$$'' followed by a digit to ``${$}''.

Changes to Tainting Checks

A bug in previous versions may have failed to detect some insecure conditions when taint checks are turned on. (Taint checks are used in setuid or setgid scripts, or when explicitly turned on with the -T invocation option.) Although it's unlikely, this may cause a previously-working script to now fail -- which should be construed as a blessing, since that indicates a potentially-serious security hole was just plugged.

New Opcode Module and Revised Safe Module

A new Opcode module supports the creation, manipulation and application of opcode masks. The revised Safe module has a new API and is implemented using the new Opcode module. Please read the new Opcode and Safe documentation.

Internal Change: FileHandle Class Based on IO::* Classes

File handles are now stored internally as type IO::Handle. The FileHandle module is still supported for backwards compatibility, but it is now merely a front end to the IO::* modules -- specifically, IO::Handle, IO::Seekable, and IO::File. We suggest, but do not require, that you use the IO::* modules in new code.

In harmony with this change, *GLOB{FILEHANDLE} is now a backward-compatible synonym for *STDOUT{IO}.

Internal Change: PerlIO internal IO abstraction interface

It is now possible to build Perl with AT&T's sfio IO package instead of stdio. See the perlapio manpage for more details, and the INSTALL file for how to use it.

New and Changed Built-in Variables

Extended error message on some platforms. (Also known as $EXTENDED_OS_ERROR if you use English).

The current set of syntax checks enabled by use strict. See the documentation of strict for more details. Not actually new, but newly documented. Because it is intended for internal use by Perl core components, there is no use English long name for this variable.

By default, running out of memory it is not trappable. However, if compiled for this, Perl may use the contents of $^M as an emergency pool after dieing with this message. Suppose that your Perl were compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then

    $^M = 'a' x (1<<16);

would allocate a 64K buffer for use when in emergency. See the INSTALL file for information on how to enable this option. As a disincentive to casual use of this advanced feature, there is no use English long name for this variable.

New and Changed Built-in Functions

delete on slices
This now works. (e.g. delete @ENV{'PATH', 'MANPATH'})

is now supported on more platforms, and prefers fcntl to lockf when emulating.

printf and sprintf
now support ``%i'' as a synonym for ``%d'', and the ``h'' modifier. So ``%hi'' means ``short integer in decimal'', and ``%ho'' means ``unsigned short integer as octal''.

keys as an lvalue
As an lvalue, keys allows you to increase the number of hash buckets allocated for the given hash. This can gain you a measure of efficiency if you know the hash is going to get big. (This is similar to pre-extending an array by assigning a larger number to $#array.) If you say

    keys %hash = 200;

then %hash will have at least 200 buckets allocated for it. These buckets will be retained even if you do %hash = ; use undef %hash if you want to free the storage while %hash is still in scope. You can't shrink the number of buckets allocated for the hash using keys in this way (but you needn't worry about doing this by accident, as trying has no effect).

my() in Control Structures
You can now use my (with or without the parentheses) in the control expressions of control structures such as:

    while (defined(my $line = <>)) {
        $line = lc $line;
    } continue {
        print $line;

    if ((my $answer = <STDIN>) =~ /^y(es)?$/i) {
    } elsif ($answer =~ /^n(o)?$/i) {
    } else {
        chomp $answer;
        die "`$answer' is neither `yes' nor `no'";

Also, you can declare a foreach loop control variable as lexical by preceding it with the word ``my''. For example, in:

    foreach my $i (1, 2, 3) {

$i is a lexical variable, and the scope of $i extends to the end of the loop, but not beyond it.

Note that you still cannot use my on global punctuation variables such as $_ and the like.

unpack() and pack()
A new format 'w' represents a BER compressed integer (as defined in ASN.1). Its format is a sequence of one or more bytes, each of which provides seven bits of the total value, with the most significant first. Bit eight of each byte is set, except for the last byte, in which bit eight is clear.

If the first argument to use is a number, it is treated as a version number instead of a module name. If the version of the Perl interpreter is less than VERSION, then an error message is printed and Perl exits immediately. Because use occurs at compile time, this check happens immediately during the compilation process, unlike require VERSION, which waits until run-time for the check. This is often useful if you need to check the current Perl version before useing library modules which have changed in incompatible ways from older versions of Perl. (We try not to do this more than we have to.)

If the VERSION argument is present between Module and LIST, then the use will call the VERSION method in class Module with the given version as an argument. The default VERSION method, inherited from the Universal class, croaks if the given version is larger than the value of the variable $Module::VERSION. (Note that there is not a comma after VERSION!)

This version-checking mechanism is similar to the one currently used in the Exporter module, but it is faster and can be used with modules that don't use the Exporter. It is the recommended method for new code.

Returns the prototype of a function as a string (or undef if the function has no prototype). FUNCTION is a reference to or the name of the function whose prototype you want to retrieve. (Not actually new; just never documented before.)

The default seed for srand, which used to be time, has been changed. Now it's a heady mix of difficult-to-predict system-dependent values, which should be sufficient for most everyday purposes.

Previous to version 5.004, calling rand without first calling srand would yield the same sequence of random numbers on most or all machines. Now, when perl sees that you're calling rand and haven't yet called srand, it calls srand with the default seed. You should still call srand manually if your code might ever be run on a pre-5.004 system, of course, or if you want a seed other than the default.

$_ as Default
Functions documented in the Camel to default to $_ now in fact do, and all those that do are so documented in the perlfunc manpage.

m//g does not trigger a pos() reset on failure
The m//g match iteration construct used to reset the iteration when it failed to match (so that the next m//g match would start at the beginning of the string). You now have to explicitly do a pos $str = 0; to reset the ``last match'' position, or modify the string in some way. This change makes it practical to chain m//g matches together in conjunction with ordinary matches using the \G zero-width assertion. See the perlop manpage and the perlre manpage.

nested sub{} closures work now
Prior to the 5.004 release, nested anonymous functions didn't work right. They do now.

formats work right on changing lexicals
Just like anonymous functions that contain lexical variables that change (like a lexical index variable for a foreach loop), formats now work properly. For example, this silently failed before, and is fine now:

    my $i;
    foreach $i ( 1 .. 10 ) {
	format =
	my i is @#

New Built-in Methods

The UNIVERSAL package automatically contains the following methods that are inherited by all other classes:

isa returns true if its object is blessed into a sub-class of CLASS

isa is also exportable and can be called as a sub with two arguments. This allows the ability to check what a reference points to. Example:

    use UNIVERSAL qw(isa);

    if(isa($ref, 'ARRAY')) {

can checks to see if its object has a method called METHOD, if it does then a reference to the sub is returned; if it does not then undef is returned.

VERSION returns the version number of the class (package). If the NEED argument is given then it will check that the current version (as defined by the $VERSION variable in the given package) not less than NEED; it will die if this is not the case. This method is normally called as a class method. This method is called automatically by the VERSION form of use.

    use A 1.2 qw(some imported subs);
    # implies:

NOTE: can directly uses Perl's internal code for method lookup, and isa uses a very similar method and caching strategy. This may cause strange effects if the Perl code dynamically changes @ISA in any package.

You may add other methods to the UNIVERSAL class via Perl or XS code. You do not need to use UNIVERSAL in order to make these methods available to your program. This is necessary only if you wish to have isa available as a plain subroutine in the current package.

TIEHANDLE Now Supported

See the perltie manpage for other kinds of ties.

This is the constructor for the class. That means it is expected to return an object of some sort. The reference can be used to hold some internal information.

    sub TIEHANDLE {
	print "<shout>\n";
	my $i;
	return bless \$i, shift;

This method will be triggered every time the tied handle is printed to. Beyond its self reference it also expects the list that was passed to the print function.

    sub PRINT {
	$r = shift;
	return print join( $, => map {uc} @_), $\;

This method will be called when the handle is read from via the read or sysread functions.

    sub READ {
	$r = shift;
	my($buf,$len,$offset) = @_;
	print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset";

This method will be called when the handle is read from. The method should return undef when there is no more data.

    sub READLINE {
	$r = shift;
	return "PRINT called $$r times\n"

GETC this
This method will be called when the getc function is called.

    sub GETC { print "Don't GETC, Get Perl"; return "a"; }

As with the other types of ties, this method will be called when the tied handle is about to be destroyed. This is useful for debugging and possibly for cleaning up.

    sub DESTROY {
	print "</shout>\n";

Malloc Enhancements

Four new compilation flags are recognized by malloc.c. (They have no effect if perl is compiled with system malloc.)

If perl is compiled with DEBUGGING_MSTATS defined, you can print memory statistics at runtime by running Perl thusly:

  env PERL_DEBUG_MSTATS=2 perl your_script_here

The value of 2 means to print statistics after compilation and on exit; with a value of 1, the statistics ares printed only on exit. (If you want the statistics at an arbitrary time, you'll need to install the optional module Devel::Peek.)

If this macro is defined, running out of memory need not be a fatal error: a memory pool can allocated by assigning to the special variable $^M. See $^M.

Perl memory allocation is by bucket with sizes close to powers of two. Because of these malloc overhead may be big, especially for data of size exactly a power of two. If PACK_MALLOC is defined, perl uses a slightly different algorithm for small allocations (up to 64 bytes long), which makes it possible to have overhead down to 1 byte for allocations which are powers of two (and appear quite often).

Expected memory savings (with 8-byte alignment in alignbytes) is about 20% for typical Perl usage. Expected slowdown due to additional malloc overhead is in fractions of a percent (hard to measure, because of the effect of saved memory on speed).

Similarly to PACK_MALLOC, this macro improves allocations of data with size close to a power of two; but this works for big allocations (starting with 16K by default). Such allocations are typical for big hashes and special-purpose scripts, especially image processing.

On recent systems, the fact that perl requires 2M from system for 1M allocation will not affect speed of execution, since the tail of such a chunk is not going to be touched (and thus will not require real memory). However, it may result in a premature out-of-memory error. So if you will be manipulating very large blocks with sizes close to powers of two, it would be wise to define this macro.

Expected saving of memory is 0-100% (100% in applications which require most memory in such 2**n chunks); expected slowdown is negligible.

Miscellaneous Efficiency Enhancements

Functions that have an empty prototype and that do nothing but return a fixed value are now inlined (e.g. sub PI { 3.14159 }).

Each unique hash key is only allocated once, no matter how many hashes have an entry with that key. So even if you have 100 copies of the same hash, the hash keys never have to be re-allocated.


Four new pragmatic modules exist:

use blib
use blib 'dir'
Looks for MakeMaker-like 'blib' directory structure starting in dir (or current directory) and working back up to five levels of parent directories.

Intended for use on command line with -M option as a way of testing arbitrary scripts against an uninstalled version of a package.

use locale
Tells the compiler to enable (or disable) the use of POSIX locales for built-in operations.

When use locale is in effect, the current LC_CTYPE locale is used for regular expressions and case mapping; LC_COLLATE for string ordering; and LC_NUMERIC for numeric formating in printf and sprintf (but not in print). LC_NUMERIC is always used in write, since lexical scoping of formats is problematic at best.

Each use locale or no locale affects statements to the end of the enclosing BLOCK or, if not inside a BLOCK, to the end of the current file. Locales can be switched and queried with POSIX::setlocale().

See the perllocale manpage for more information.

use ops
Disable unsafe opcodes, or any named opcodes, when compiling Perl code.

use vmsish
Enable VMS-specific language features. Currently, there are three VMS-specific features available: 'status', which makes $? and system return genuine VMS status values instead of emulating POSIX; 'exit', which makes exit take a genuine VMS status value instead of assuming that exit 1 is an error; and 'time', which makes all times relative to the local time zone, in the VMS tradition.


Installation Directories

The installperl script now places the Perl source files for extensions in the architecture-specific library directory, which is where the shared libraries for extensions have always been. This change is intended to allow administrators to keep the Perl 5.004 library directory unchanged from a previous version, without running the risk of binary incompatibility between extensions' Perl source and shared libraries.


New constants in the existing Fcntl modules are now supported, provided that your operating system happens to support them:


These constants are intended for use with the Perl operators sysopen and fcntl and the basic database modules like SDBM_File. For the exact meaning of these and other Fcntl constants please refer to your operating system's documentation for fcntl and open.

In addition, the Fcntl module now provides these constants for use with the Perl operator flock:


These constants are defined in all environments (because where there is no flock system call, Perl emulates it). However, for historical reasons, these constants are not exported unless they are explicitly requested with the ``:flock'' tag (e.g. use Fcntl ':flock').

Module Information Summary

Brand new modules, arranged by topic rather than strictly alphabetically:

    CPAN                 interface to Comprehensive Perl Archive Network
    CPAN::FirstTime      create a CPAN configuration file
    CPAN::Nox            run CPAN while avoiding compiled extensions                Top-level interface to IO::* classes
    IO/           IO::File extension Perl module
    IO/         IO::Handle extension Perl module
    IO/           IO::Pipe extension Perl module
    IO/       IO::Seekable extension Perl module
    IO/         IO::Select extension Perl module
    IO/         IO::Socket extension Perl module            Disable named opcodes when compiling Perl code

    ExtUtils/    Utilities for embedding Perl in C programs
    ExtUtils/  Fixes up @INC to use just-built extension           Find path of currently executing program

    Class/    Structure/member template builder
    File/         Object-oriented wrapper around CORE::stat
    Net/       Object-oriented wrapper around CORE::gethost*
    Net/        Object-oriented wrapper around CORE::getnet*
    Net/      Object-oriented wrapper around CORE::getproto*
    Net/       Object-oriented wrapper around CORE::getserv*
    Time/       Object-oriented wrapper around CORE::gmtime
    Time/    Object-oriented wrapper around CORE::localtime
    Time/           Perl implementation of "struct tm" for {gm,local}time
    User/        Object-oriented wrapper around CORE::getgr*
    User/        Object-oriented wrapper around CORE::getpw*

    Tie/       Base class for tied hashes with references as keys         Base class for *ALL* classes


The IO module provides a simple mechanism to load all of the IO modules at one go. Currently this includes:


For more information on any of these modules, please see its respective documentation.


The Math::Complex module has been totally rewritten, and now supports more operations. These are overloaded:

     + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify)

And these functions are now exported:

    pi i Re Im arg
    log10 logn cbrt root
    tan cotan asin acos atan acotan
    sinh cosh tanh cotanh asinh acosh atanh acotanh
    cplx cplxe


There have been quite a few changes made to DB_File. Here are a few of the highlights:

Refer to the HISTORY section in for a complete list of changes. Everything after DB_File 1.01 has been added since 5.003.


Major rewrite - support added for both udp echo and real icmp pings.

Overridden Built-ins

Many of the Perl built-ins returning lists now have object-oriented overrides. These are:


For example, you can now say

    use File::stat;
    use User::pwent;
    $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid);

Utility Changes


void XSUBs now default to returning nothing
Due to a documentation/implementation bug in previous versions of Perl, XSUBs with a return type of void have actually been returning one value. Usually that value was the GV for the XSUB, but sometimes it was some already freed or reused value, which would sometimes lead to program failure.

In Perl 5.004, if an XSUB is declared as returning void, it actually returns no value, i.e. an empty list (though there is a backward-compatibility exception; see below). If your XSUB really does return an SV, you should give it a return type of SV *.

For backward compatibility, xsubpp tries to guess whether a void XSUB is really void or if it wants to return an SV *. It does so by examining the text of the XSUB: if xsubpp finds what looks like an assignment to ST, it assumes that the XSUB's return type is really SV *.

C Language API Changes

gv_fetchmethod and perl_call_sv
The gv_fetchmethod function finds a method for an object, just like in Perl 5.003. The GV it returns may be a method cache entry. However, in Perl 5.004, method cache entries are not visible to users; therefore, they can no longer be passed directly to perl_call_sv. Instead, you should use the GvCV macro on the GV to extract its CV, and pass the CV to perl_call_sv.

The most likely symptom of passing the result of gv_fetchmethod to perl_call_sv is Perl's producing an ``Undefined subroutine called'' error on the second call to a given method (since there is no cache on the first call).

Extended API for manipulating hashes
Internal handling of hash keys has changed. The old hashtable API is still fully supported, and will likely remain so. The additions to the API allow passing keys as SV*s, so that tied hashes can be given real scalars as keys rather than plain strings (non-tied hashes still can only use strings as keys). New extensions must use the new hash access functions and macros if they wish to use SV* keys. These additions also make it feasible to manipulate HE*s (hash entries), which can be more efficient. See the perlguts manpage for details.

Documentation Changes

Many of the base and library pods were updated. These new pods are included in section 1:

This document.

Locale support (internationalization and localization).

Tutorial on Perl OO programming.

Perl internal IO abstraction interface.

Although not new, this has been massively updated.

Although not new, this has been massively updated.

New Diagnostics

Several new conditions will trigger warnings that were silent before. Some only affect certain platforms. The following new warnings and errors outline these. These messages are classified as follows (listed in increasing order of desperation):

   (W) A warning (optional).
   (D) A deprecation (optional).
   (S) A severe warning (mandatory).
   (F) A fatal error (trappable).
   (P) An internal error you should never see (trappable).
   (X) A very fatal error (non-trappable).
   (A) An alien error message (not generated by Perl).

"my" variable %s masks earlier declaration in same scope
(S) A lexical variable has been redeclared in the same scope, effectively eliminating all access to the previous instance. This is almost always a typographical error. Note that the earlier variable will still exist until the end of the scope or until all closure referents to it are destroyed.

%s argument is not a HASH element or slice
(F) The argument to delete must be either a hash element, such as


or a hash slice, such as

    @foo{$bar, $baz, $xyzzy}
    @{$ref->[12]}{"susie", "queue"}

Allocation too large: %lx
(X) You can't allocate more than 64K on an MSDOS machine.

Allocation too large
(F) You can't allocate more than 2^31+``small amount'' bytes.

Attempt to free non-existent shared string
(P) Perl maintains a reference counted internal table of strings to optimize the storage and access of hash keys and other strings. This indicates someone tried to decrement the reference count of a string that can no longer be found in the table.

Attempt to use reference as lvalue in substr
(W) You supplied a reference as the first argument to substr used as an lvalue, which is pretty strange. Perhaps you forgot to dereference it first. See substr.

Unsupported function fork
(F) Your version of executable does not support forking.

Note that under some systems, like OS/2, there may be different flavors of Perl executables, some of which may support fork, some not. Try changing the name you call Perl by to perl_, perl__, and so on.

Ill-formed logical name |%s| in prime_env_iter
(W) A warning peculiar to VMS. A logical name was encountered when preparing to iterate over %ENV which violates the syntactic rules governing logical names. Since it cannot be translated normally, it is skipped, and will not appear in %ENV. This may be a benign occurrence, as some software packages might directly modify logical name tables and introduce non-standard names, or it may indicate that a logical name table has been corrupted.

Can't use bareword ("%s") as %s ref while "strict refs" in use
(F) Only hard references are allowed by ``strict refs''. Symbolic references are disallowed. See the perlref manpage.

Constant subroutine %s redefined
(S) You redefined a subroutine which had previously been eligible for inlining. See Constant Functions for commentary and workarounds.

(F) You passed die an empty string (the equivalent of die "") or you called it with no args and both $@ and $_ were empty.

Integer overflow in hex number
(S) The literal hex number you have specified is too big for your architecture. On a 32-bit architecture the largest hex literal is 0xFFFFFFFF.

Integer overflow in octal number
(S) The literal octal number you have specified is too big for your architecture. On a 32-bit architecture the largest octal literal is 037777777777.

Name "%s::%s" used only once: possible typo
(W) Typographical errors often show up as unique variable names. If you had a good reason for having a unique name, then just mention it again somehow to suppress the message (the use vars pragma is provided for just this purpose).

Null picture in formline
(F) The first argument to formline must be a valid format picture specification. It was found to be empty, which probably means you supplied it an uninitialized value. See the perlform manpage.

Offset outside string
(F) You tried to do a read/write/send/recv operation with an offset pointing outside the buffer. This is difficult to imagine. The sole exception to this is that sysreading past the buffer will extend the buffer and zero pad the new area.

Stub found while resolving method `%s' overloading `%s' in package `%s'
(P) Overloading resolution over @ISA tree may be broken by importing stubs. Stubs should never be implicitely created, but explicit calls to can may break this.

Cannot resolve method `%s' overloading `%s' in package `s'
(P) Internal error trying to resolve overloading specified by a method name (as opposed to a subroutine reference).

Out of memory!
(X|F) The malloc function returned 0, indicating there was insufficient remaining memory (or virtual memory) to satisfy the request.

The request was judged to be small, so the possibility to trap it depends on the way Perl was compiled. By default it is not trappable. However, if compiled for this, Perl may use the contents of $^M as an emergency pool after dieing with this message. In this case the error is trappable once.

Out of memory during request for %s
(F) The malloc function returned 0, indicating there was insufficient remaining memory (or virtual memory) to satisfy the request. However, the request was judged large enough (compile-time default is 64K), so a possibility to shut down by trapping this error is granted.

Possible attempt to put comments in qw() list
(W) qw lists contain items separated by whitespace; as with literal strings, comment characters are not ignored, but are instead treated as literal data. (You may have used different delimiters than the exclamation marks parentheses shown here; braces are also frequently used.)

You probably wrote something like this:

    @list = qw(
        a # a comment
        b # another comment

when you should have written this:

    @list = qw(

If you really want comments, build your list the old-fashioned way, with quotes and commas:

    @list = (
        'a',    # a comment
        'b',    # another comment

Possible attempt to separate words with commas
(W) qw lists contain items separated by whitespace; therefore commas aren't needed to separate the items. (You may have used different delimiters than the parentheses shown here; braces are also frequently used.)

You probably wrote something like this:

    qw! a, b, c !;

which puts literal commas into some of the list items. Write it without commas if you don't want them to appear in your data:

    qw! a b c !;

Scalar value @%s{%s} better written as $%s{%s}
(W) You've used a hash slice (indicated by @) to select a single element of a hash. Generally it's better to ask for a scalar value (indicated by $). The difference is that $foo{&bar} always behaves like a scalar, both when assigning to it and when evaluating its argument, while @foo{&bar} behaves like a list when you assign to it, and provides a list context to its subscript, which can do weird things if you're expecting only one subscript.

untie attempted while %d inner references still exist
(W) A copy of the object returned from tie (or tied) was still valid when untie was called.

Value of %s construct can be "0"; test with defined()
(W) In a conditional expression, you used < HANDLE>, <*> (glob), or readdir as a boolean value. Each of these constructs can return a value of ``0''; that would make the conditional expression false, which is probably not what you intended. When using these constructs in conditional expressions, test their values with the defined operator.

Variable "%s" may be unavailable
(W) An inner (nested) anonymous subroutine is inside a named subroutine, and outside that is another subroutine; and the anonymous (innermost) subroutine is referencing a lexical variable defined in the outermost subroutine. For example:

   sub outermost { my $a; sub middle { sub { $a } } }

If the anonymous subroutine is called or referenced (directly or indirectly) from the outermost subroutine, it will share the variable as you would expect. But if the anonymous subroutine is called or referenced when the outermost subroutine is not active, it will see the value of the shared variable as it was before and during the *first* call to the outermost subroutine, which is probably not what you want.

In these circumstances, it is usually best to make the middle subroutine anonymous, using the sub {} syntax. Perl has specific support for shared variables in nested anonymous subroutines; a named subroutine in between interferes with this feature.

Variable "%s" will not stay shared
(W) An inner (nested) named subroutine is referencing a lexical variable defined in an outer subroutine.

When the inner subroutine is called, it will probably see the value of the outer subroutine's variable as it was before and during the *first* call to the outer subroutine; in this case, after the first call to the outer subroutine is complete, the inner and outer subroutines will no longer share a common value for the variable. In other words, the variable will no longer be shared.

Furthermore, if the outer subroutine is anonymous and references a lexical variable outside itself, then the outer and inner subroutines will never share the given variable.

This problem can usually be solved by making the inner subroutine anonymous, using the sub {} syntax. When inner anonymous subs that reference variables in outer subroutines are called or referenced, they are automatically re-bound to the current values of such variables.

Warning: something's wrong
(W) You passed warn an empty string (the equivalent of warn "") or you called it with no args and $_ was empty.

Got an error from DosAllocMem
(P) An error peculiar to OS/2. Most probably you're using an obsolete version of Perl, and this should not happen anyway.

(F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form



    prefix1 prefix2

with non-empty prefix1 and prefix2. If prefix1 is indeed a prefix of a builtin library search path, prefix2 is substituted. The error may appear if components are not found, or are too long. See perlos2.

PERL_SH_DIR too long
(F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the sh-shell in. See perlos2.

Process terminated by SIG%s
(W) This is a standard message issued by OS/2 applications, while *nix applications die in silence. It is considered a feature of the OS/2 port. One can easily disable this by appropriate sighandlers, see Signals. See perlos2.


If you find what you think is a bug, you might check the headers of recently posted articles in the comp.lang.perl.misc newsgroup. There may also be information at, the Perl Home Page.

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 <> 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. This file has been significantly updated for 5.004, so even veteran users should look through it.

The README file for general stuff.

The Copying file for copyright information.


Constructed by Tom Christiansen, grabbing material with permission from innumerable contributors, with kibitzing by more than a few Perl porters.

Last update: Sat Mar 8 19:51:26 EST 1997