List assignment to %ENV works¶

"%ENV = ()" and "%ENV = @list" now work as expected (except on VMS where it generates a fatal error).

Change to "Can't locate Foo.pm in @INC" error¶

The error "Can't locate Foo.pm in @INC" now lists the contents of @INC for easier debugging.

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.

$PERL5OPT environment variable¶

You may now put Perl options in the $PERL5OPT environment variable. Unless Perl is running with taint checks, it will interpret this variable as if its contents had appeared on a "#!perl" line at the beginning of your script, except that hyphens are optional. PERL5OPT may only be used to set the following switches: -[DIMUdmw].

Limitations on -M, -m, and -T options¶

The "-M" and "-m" options are no longer allowed on the "#!" line of a script. If a script needs a module, it should invoke it with the "use" pragma.

The -T option is also forbidden on the "#!" line of a script, unless it was present on the Perl command line. Due to the way "#!" works, this usually means that -T must be in the first argument. Thus:

    #!/usr/bin/perl -T -w

will probably work for an executable script invoked as "scriptname", while:

    #!/usr/bin/perl -w -T

will probably fail under the same conditions. (Non-Unix systems will probably not follow this rule.) But "perl scriptname" is guaranteed to fail, since then there is no chance of -T being found on the command line before it is found on the "#!" line.

More precise warnings¶

If you removed the -w option from your Perl 5.003 scripts because it made Perl too verbose, we recommend that you try putting it back when you upgrade to Perl 5.004. Each new perl version tends to remove some undesirable warnings, while adding new warnings that may catch bugs in your scripts.

Deprecated: Inherited "AUTOLOAD" for non-methods¶

Before Perl 5.004, "AUTOLOAD" functions were looked up as methods (using the @ISA hierarchy), even when the function to be autoloaded was called as a plain function (e.g. "Foo::bar()"), not a method (e.g. "Foo->bar()" or "$obj->bar()").

Perl 5.005 will use method lookup only for methods' "AUTOLOAD"s. However, there is a significant base of existing code that may be using the old behavior. So, as an interim step, Perl 5.004 issues an optional warning when a non-method uses an inherited "AUTOLOAD".

The simple rule is: Inheritance will not work when autoloading non-methods. The simple fix for old code is: In any module that used to depend on inheriting "AUTOLOAD" for non-methods from a base class named "BaseClass", execute "*AUTOLOAD = \&BaseClass::AUTOLOAD" during startup.

Previously deprecated %OVERLOAD is no longer usable¶

Using %OVERLOAD to define overloading was deprecated in 5.003. Overloading is now defined using the overload pragma. %OVERLOAD is still used internally but should not be used by Perl scripts. See overload for more details.

Subroutine arguments created only when they're modified¶

In Perl 5.004, nonexistent array and hash elements used as subroutine parameters are brought into existence only if they are actually assigned to (via @_).

Earlier versions of Perl vary in their handling of such arguments. Perl versions 5.002 and 5.003 always brought them into existence. Perl versions 5.000 and 5.001 brought them into existence only if they were not the first argument (which was almost certainly a bug). Earlier versions of Perl never brought them into existence.

For example, given this code:

     undef @a; undef %a;
     sub show { print $_[0] };
     sub change { $_[0]++ };
     show($a[2]);
     change($a{b});

After this code executes in Perl 5.004, $a{b} exists but $a[2] does not. In Perl 5.002 and 5.003, both $a{b} and $a[2] would have existed (but $a[2]'s value would have been undefined).

Group vector changeable with $)¶

The $) special variable has always (well, in Perl 5, at least) reflected not only the current effective group, but also the group list as returned by the "getgroups()" C function (if there is one). However, until this release, there has not been a way to call the "setgroups()" C function from Perl.

In Perl 5.004, assigning to $) is exactly symmetrical with examining it: The first number in its string value is used as the effective gid; if there are any numbers after the first one, they are passed to the "setgroups()" C function (if there is one).

Fixed parsing of $$<digit>, &$<digit>, etc.¶

Perl versions before 5.004 misinterpreted any type marker followed by "$" and a digit. For example, "$$0" was incorrectly taken to mean "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.

However, the developers of Perl 5.004 could not fix this bug completely, because at least two widely-used modules depend on the old meaning of "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the old (broken) way inside strings; but it generates this message as a warning. And in Perl 5.005, this special treatment will cease.

Fixed localization of $<digit>, $&, etc.¶

Perl versions before 5.004 did not always properly localize the regex-related special variables. Perl 5.004 does localize them, as the documentation has always said it should. This may result in $1, $2, etc. no longer being set where existing programs use them.

No resetting of $. on implicit close¶

The documentation for Perl 5.0 has always stated that $. is not reset when an already-open file handle is reopened with no intervening call to "close". Due to a bug, perl versions 5.000 through 5.003 did reset $. under that circumstance; Perl 5.004 does not.

"wantarray" may return undef¶

The "wantarray" operator returns true if a subroutine is expected to return a list, and false otherwise. In Perl 5.004, "wantarray" can also return the undefined value if a subroutine's return value will not be used at all, which allows subroutines to avoid a time-consuming calculation of a return value if it isn't going to be used.

"eval EXPR" determines value of EXPR in scalar context¶

Perl (version 5) used to determine the value of EXPR inconsistently, sometimes incorrectly using the surrounding context for the determination. Now, the value of EXPR (before being parsed by eval) is always determined in a scalar context. Once parsed, it is executed as before, by providing the context that the scope surrounding the eval provided. This change makes the behavior Perl4 compatible, besides fixing bugs resulting from the inconsistent behavior. This program:

    @a = qw(time now is time);
    print eval @a;
    print '|', scalar eval @a;

used to print something like "timenowis881399109|4", but now (and in perl4) prints "4|4".

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.

The new restrictions when tainting include:

No glob() or <*>

These operators may spawn the C shell (csh), which cannot be made safe. This restriction will be lifted in a future version of Perl when globbing is implemented without the use of an external program.

No spawning if tainted $CDPATH, $ENV, $BASH_ENV

These environment variables may alter the behavior of spawned programs (especially shells) in ways that subvert security. So now they are treated as dangerous, in the manner of $IFS and $PATH.

No spawning if tainted $TERM doesn't look like a terminal name

Some termcap libraries do unsafe things with $TERM. However, it would be unnecessarily harsh to treat all $TERM values as unsafe, since only shell metacharacters can cause trouble in $TERM. So a tainted $TERM is considered to be safe if it contains only alphanumerics, underscores, dashes, and colons, and unsafe if it contains other characters (including whitespace).

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.

Embedding improvements¶

In older versions of Perl it was not possible to create more than one Perl interpreter instance inside a single process without leaking like a sieve and/or crashing. The bugs that caused this behavior have all been fixed. However, you still must take care when embedding Perl in a C program. See the updated perlembed manpage for tips on how to manage your interpreters.

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 just a backward-compatible synonym for *GLOB{IO}.

Internal change: PerlIO abstraction interface¶

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

New and changed syntax¶

$coderef->(PARAMS)

A subroutine reference may now be suffixed with an arrow and a (possibly empty) parameter list. This syntax denotes a call of the referenced subroutine, with the given parameters (if any).

This new syntax follows the pattern of "$hashref->{FOO}" and "$aryref->[$foo]": You may now write "&$subref($foo)" as "$subref->($foo)". All these arrow terms may be chained; thus, "&{$table->{FOO}}($bar)" may now be written "$table->{FOO}->($bar)".

New and changed builtin constants¶

__PACKAGE__

The current package name at compile time, or the undefined value if there is no current package (due to a "package;" directive). Like "__FILE__" and "__LINE__", "__PACKAGE__" does not interpolate into strings.

New and changed builtin variables¶

$^E

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

$^H

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.

$^M

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 die()ing with this message. Suppose that your Perl were compiled with -DPERL_EMERGENCY_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 builtin functions¶

delete on slices

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

flock

is now supported on more platforms, prefers fcntl to lockf when emulating, and always flushes before (un)locking.

printf and sprintf

Perl now implements these functions itself; it doesn't use the C library function sprintf() any more, except for floating-point numbers, and even then only known flags are allowed. As a result, it is now possible to know which conversions and flags will work, and what they will do.

The new conversions in Perl's sprintf() are:

   %i   a synonym for %d
   %p   a pointer (the address of the Perl value, in hexadecimal)
   %n   special: *stores* the number of characters output so far
        into the next variable in the parameter list
    

The new flags that go between the "%" and the conversion are:

   #    prefix octal with "0", hex with "0x"
   h    interpret integer as C type "short" or "unsigned short"
   V    interpret integer as Perl's standard integer type
    

Also, where a number would appear in the flags, an asterisk ("*") may be used instead, in which case Perl uses the next item in the parameter list as the given number (that is, as the field width or precision). If a field width obtained through "*" is negative, it has the same effect as the '-' flag: left-justification.

See "sprintf" in perlfunc for a complete list of conversion and flags.

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) {
        user_agrees();
    } elsif ($answer =~ /^n(o)?$/i) {
        user_disagrees();
    } 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) {
        some_function();
    }
    

$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.

pack() and unpack()

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 'p' or 'P' are given undef as values, they now generate a NULL pointer.

Both pack() and unpack() now fail when their templates contain invalid types. (Invalid types used to be ignored.)

sysseek()

The new sysseek() operator is a variant of seek() that sets and gets the file's system read/write position, using the lseek(2) system call. It is the only reliable way to seek before using sysread() or syswrite(). Its return value is the new position, or the undefined value on failure.

use VERSION

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 runtime for the check. This is often useful if you need to check the current Perl version before "use"ing library modules which have changed in incompatible ways from older versions of Perl. (We try not to do this more than we have to.)

use Module VERSION LIST

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.

prototype(FUNCTION)

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.)

srand

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 perlfunc.

"m//gc" does not reset search position on failure

The "m//g" match iteration construct has always reset its target string's search position (which is visible through the "pos" operator) when a match fails; as a result, the next "m//g" match after a failure starts again at the beginning of the string. With Perl 5.004, this reset may be disabled by adding the "c" (for "continue") modifier, i.e. "m//gc". This feature, in conjunction with the "\G" zero-width assertion, makes it possible to chain matches together. See perlop and perlre.

"m//x" ignores whitespace before ?*+{}

The "m//x" construct has always been intended to ignore all unescaped whitespace. However, before Perl 5.004, whitespace had the effect of escaping repeat modifiers like "*" or "?"; for example, "/a *b/x" was (mis)interpreted as "/a\*b/x". This bug has been fixed in 5.004.

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 (printed only zeros), but is fine now:

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

However, it still fails (without a warning) if the foreach is within a subroutine:

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

New builtin methods¶

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

isa(CLASS)

"isa" returns true if its object is blessed into a subclass 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(METHOD)

"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( [NEED] )

"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:
    A->VERSION(1.2);
    

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 perltie for other kinds of tie()s.

TIEHANDLE classname, LIST

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;
    }
    

PRINT this, LIST

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

PRINTF this, LIST

This method will be triggered every time the tied handle is printed to with the "printf()" function. Beyond its self reference it also expects the format and list that was passed to the printf function.

    sub PRINTF {
        shift;
          my $fmt = shift;
        print sprintf($fmt, @_)."\n";
    }
    

READ this LIST

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";
    }
    

READLINE this

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"; }
    

DESTROY this

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¶

If perl is compiled with the malloc included with the perl distribution (that is, if "perl -V:d_mymalloc" is 'define') then 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 are printed only on exit. (If you want the statistics at an arbitrary time, you'll need to install the optional module Devel::Peek.)

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

-DPERL_EMERGENCY_SBRK

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".

-DPACK_MALLOC

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).

-DTWO_POT_OPTIMIZE

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 reallocated.

Win32¶

Perl 5.004 now includes support for building a "native" perl under Windows NT, using the Microsoft Visual C++ compiler (versions 2.0 and above) or the Borland C++ compiler (versions 5.02 and above). The resulting perl can be used under Windows 95 (if it is installed in the same directory locations as it got installed in Windows NT). This port includes support for perl extension building tools like ExtUtils::MakeMaker and h2xs, so that many extensions available on the Comprehensive Perl Archive Network (CPAN) can now be readily built under Windows NT. See http://www.perl.com/ for more information on CPAN and README.win32 in the perl distribution for more details on how to get started with building this port.

There is also support for building perl under the Cygwin32 environment. Cygwin32 is a set of GNU tools that make it possible to compile and run many Unix programs under Windows NT by providing a mostly Unix-like interface for compilation and execution. See README.cygwin32 in the perl distribution for more details on this port and how to obtain the Cygwin32 toolkit.

Plan 9¶

See README.plan9 in the perl distribution.

QNX¶

See README.qnx in the perl distribution.

AmigaOS¶

See README.amigaos in the perl distribution.

Required Updates¶

Though Perl 5.004 is compatible with almost all modules that work with Perl 5.003, there are a few exceptions:

    Module   Required Version for Perl 5.004
    ------   -------------------------------
    Filter   Filter-1.12
    LWP      libwww-perl-5.08
    Tk       Tk400.202 (-w makes noise)

Also, the majordomo mailing list program, version 1.94.1, doesn't work with Perl 5.004 (nor with perl 4), because it executes an invalid regular expression. This bug is fixed in majordomo version 1.94.2.

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.

Module information summary¶

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

    CGI.pm               Web server interface ("Common Gateway Interface")
    CGI/Apache.pm        Support for Apache's Perl module
    CGI/Carp.pm          Log server errors with helpful context
    CGI/Fast.pm          Support for FastCGI (persistent server process)
    CGI/Push.pm          Support for server push
    CGI/Switch.pm        Simple interface for multiple server types
    CPAN                 Interface to Comprehensive Perl Archive Network
    CPAN::FirstTime      Utility for creating CPAN configuration file
    CPAN::Nox            Runs CPAN while avoiding compiled extensions
    IO.pm                Top-level interface to IO::* classes
    IO/File.pm           IO::File extension Perl module
    IO/Handle.pm         IO::Handle extension Perl module
    IO/Pipe.pm           IO::Pipe extension Perl module
    IO/Seekable.pm       IO::Seekable extension Perl module
    IO/Select.pm         IO::Select extension Perl module
    IO/Socket.pm         IO::Socket extension Perl module
    Opcode.pm            Disable named opcodes when compiling Perl code
    ExtUtils/Embed.pm    Utilities for embedding Perl in C programs
    ExtUtils/testlib.pm  Fixes up @INC to use just-built extension
    FindBin.pm           Find path of currently executing program
    Class/Struct.pm      Declare struct-like datatypes as Perl classes
    File/stat.pm         By-name interface to Perl's builtin stat
    Net/hostent.pm       By-name interface to Perl's builtin gethost*
    Net/netent.pm        By-name interface to Perl's builtin getnet*
    Net/protoent.pm      By-name interface to Perl's builtin getproto*
    Net/servent.pm       By-name interface to Perl's builtin getserv*
    Time/gmtime.pm       By-name interface to Perl's builtin gmtime
    Time/localtime.pm    By-name interface to Perl's builtin localtime
    Time/tm.pm           Internal object for Time::{gm,local}time
    User/grent.pm        By-name interface to Perl's builtin getgr*
    User/pwent.pm        By-name interface to Perl's builtin getpw*
    Tie/RefHash.pm       Base class for tied hashes with references as keys
    UNIVERSAL.pm         Base class for *ALL* classes

Fcntl¶

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

    F_GETOWN F_SETOWN
    O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC
    O_EXLOCK O_SHLOCK

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():

        LOCK_SH LOCK_EX LOCK_NB LOCK_UN

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'").

IO¶

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

     IO::Handle
     IO::Seekable
     IO::File
     IO::Pipe
     IO::Socket

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

Math::Complex¶

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 ln cbrt root
    tan
    csc sec cot
    asin acos atan
    acsc asec acot
    sinh cosh tanh
    csch sech coth
    asinh acosh atanh
    acsch asech acoth
    cplx cplxe

Math::Trig¶

This new module provides a simpler interface to parts of Math::Complex for those who need trigonometric functions only for real numbers.

DB_File¶

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

• Fixed a handful of bugs.
• By public demand, added support for the standard hash function exists().
• Made it compatible with Berkeley DB 1.86.
• Made negative subscripts work with RECNO interface.
• Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default mode from 0640 to 0666.
• Made DB_File automatically import the open() constants (O_RDWR, O_CREAT etc.) from Fcntl, if available.
• Updated documentation.

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

Net::Ping¶

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

Object-oriented overrides for builtin operators¶

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

    File::stat
    Net::hostent
    Net::netent
    Net::protoent
    Net::servent
    Time::gmtime
    Time::localtime
    User::grent
    User::pwent

For example, you can now say

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

pod2html¶

Sends converted HTML to standard output

The pod2html utility included with Perl 5.004 is entirely new. By default, it sends the converted HTML to its standard output, instead of writing it to a file like Perl 5.003's pod2html did. Use the --outfile=FILENAME option to write to a file.

xsubpp¶

"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(0), it assumes that the XSUB's return type is really "SV *".