NAME
    perldelta - what's new for perl5.004

DESCRIPTION
    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, Plan 9, LynxOS, VMS,
    OS/2, QNX, AmigaOS, and Windows NT. Perl runs on Windows 95 as
    well, but it cannot be built there, for lack of a reasonable
    command interpreter.

Core Changes
    Most importantly, many bugs were fixed, including several
    security problems. See the Changes file in the distribution for
    details.

  List assignment to %ENV works

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

  "Can't locate Foo.pm in @INC" error now lists @INC

  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 the overload manpage 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 the perlapio manpage 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->($foo)'. All of these arrow terms may be chained;
        thus, `&{$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 the "sprintf" entry in the perlfunc manpage 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 the
        perlfunc manpage.

    `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 the perlop manpage and the perlre manpage.

    `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 the perltie manpage 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 `$^M'. See the section on "$^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.

Support for More Operating Systems
    Support for the following operating systems is new in Perl
    5.004.

  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 the MakeMaker manpage and the h2xs
    manpage, 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.

Pragmata
    Six new pragmatic modules exist:

    use autouse MODULE => qw(sub1 sub2 sub3)
        Defers `require MODULE' until someone calls one of the
        specified subroutines (which must be exported by MODULE).
        This pragma should be used with caution, and only when
        necessary.

    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 constant NAME => VALUE
        Provides a convenient interface for creating compile-time
        constants, See the section on "Constant Functions" in the
        perlsub manpage.

    use locale
        Tells the compiler to enable (or disable) the use of POSIX
        locales for builtin 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.


Modules
  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 of 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);


Utility Changes
  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 *'.


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).

    `perl_eval_pv'
        A new function handy for eval'ing strings of Perl code
        inside C code. This function returns the value from the eval
        statement, which can be used instead of fetching globals
        from the symbol table. See the perlguts manpage, the
        perlembed manpage and the perlcall manpage for details and
        examples.

    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 (nontied 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:

    the perldelta manpage
        This document.

    the perlfaq manpage
        Frequently asked questions.

    the perllocale manpage
        Locale support (internationalization and localization).

    the perltoot manpage
        Tutorial on Perl OO programming.

    the perlapio manpage
        Perl internal IO abstraction interface.

    the perlmodlib manpage
        Perl module library and recommended practice for module
        creation. Extracted from the perlmod manpage (which is much
        smaller as a result).

    the perldebug manpage
        Although not new, this has been massively updated.

    the perlsec manpage
        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 (nontrappable).
       (A) An alien error message (not generated by Perl).


    "my" variable %s masks earlier declaration in same scope
        (W) 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

            $foo{$bar}
            $ref->[12]->{"susie"}


        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 MS-DOS machine.

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

    Applying %s to %s will act on scalar(%s)
        (W) The pattern match (//), substitution (s///), and
        transliteration (tr///) operators work on scalar values. If
        you apply one of them to an array or a hash, it will convert
        the array or hash to a scalar value -- the length of an
        array, or the population info of a hash -- and then work on
        that scalar value. This is probably not what you meant to
        do. See the "grep" entry in the perlfunc manpage and the
        "map" entry in the perlfunc manpage for alternatives.

    Attempt to free nonexistent 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 the "substr" entry
        in the perlfunc manpage.

    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 redefine active sort subroutine %s
        (F) Perl optimizes the internal handling of sort subroutines
        and keeps pointers into them. You tried to redefine one such
        sort subroutine when it was currently active, which is not
        allowed. If you really want to do this, you should write
        `sort { &func } @x' instead of `sort func @x'.

    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.

    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).

    Constant subroutine %s redefined
        (S) You redefined a subroutine which had previously been
        eligible for inlining. See the section on "Constant
        Functions" in the perlsub manpage for commentary and
        workarounds.

    Constant subroutine %s undefined
        (S) You undefined a subroutine which had previously been
        eligible for inlining. See the section on "Constant
        Functions" in the perlsub manpage for commentary and
        workarounds.

    Copy method did not return a reference
        (F) The method which overloads "=" is buggy. See the "Copy
        Constructor" entry in the overload manpage.

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

    Exiting pseudo-block via %s
        (W) You are exiting a rather special block construct (like a
        sort block or subroutine) by unconventional means, such as a
        goto, or a loop control statement. See the "sort" entry in
        the perlfunc manpage.

    Identifier too long
        (F) Perl limits identifiers (names for variables, functions,
        etc.) to 252 characters for simple names, somewhat more for
        compound names (like `$A::B'). You've exceeded Perl's
        limits. Future versions of Perl are likely to eliminate
        these arbitrary limitations.

    Illegal character %s (carriage return)
        (F) A carriage return character was found in the input. This
        is an error, and not a warning, because carriage return
        characters can break multi-line strings, including here
        documents (e.g., `print <<EOF;').

    Illegal switch in PERL5OPT: %s
        (X) The PERL5OPT environment variable may only be used to
        set the following switches: -[DIMUdmw].

    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.

    internal error: glob failed
        (P) Something went wrong with the external program(s) used
        for `glob' and `<*.c>'. This may mean that your csh (C
        shell) is broken. If so, you should change all of the csh-
        related variables in config.sh: If you have tcsh, make the
        variables refer to it as if it were csh (e.g.
        `full_csh='/usr/bin/tcsh''); otherwise, make them all empty
        (except that `d_csh' should be `'undef'') so that Perl will
        think csh is missing. In either case, after editing
        config.sh, run `./Configure -S' and rebuild Perl.

    Invalid conversion in %s: "%s"
        (W) Perl does not understand the given format conversion.
        See the "sprintf" entry in the perlfunc manpage.

    Invalid type in pack: '%s'
        (F) The given character is not a valid pack type. See the
        "pack" entry in the perlfunc manpage.

    Invalid type in unpack: '%s'
        (F) The given character is not a valid unpack type. See the
        "unpack" entry in the perlfunc manpage.

    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 `sysread()'ing
        past the buffer will extend the buffer and zero pad the new
        area.

    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
        die()ing 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.

    panic: frexp
        (P) The library function frexp() failed, making printf("%f")
        impossible.

    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 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(
                a
                b
            );


        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.

    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.

    Too late for "-T" option
        (X) The #! line (or local equivalent) in a Perl script
        contains the -T option, but Perl was not invoked with -T in
        its argument list. This is an error because, by the time
        Perl discovers a -T in a script, it's too late to properly
        taint everything from the environment. So Perl gives up.

    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.

    Unrecognized character %s
        (F) The Perl parser has no idea what to do with the
        specified character in your Perl script (or eval). Perhaps
        you tried to run a compressed script, a binary program, or a
        directory as a Perl program.

    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.

    Use of "$$<digit>" to mean "${$}<digit>" is deprecated
        (D) Perl versions before 5.004 misinterpreted any type
        marker followed by "$" and a digit. For example, "$$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.

    Value of %s can be "0"; test with defined()
        (W) In a conditional expression, you used <HANDLE>, <*>
        (glob), `each()', 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 rebound 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.

    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 nonstandard names, or it may indicate that a
        logical name table has been corrupted.

    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.

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

            prefix1;prefix2


        or

            prefix1 prefix2


        with nonempty 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 "PERLLIB_PREFIX" in README.os2.

    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 "PERL_SH_DIR" in README.os2.

    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 the section on "Signals" in the
        perlipc manpage. See also "Process terminated by
        SIGTERM/SIGINT" in README.os2.


BUGS
    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
    http://www.perl.com/perl/, 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
    <perlbug@perl.com> to be analysed by the Perl porting team.

SEE ALSO
    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.

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

    Last update: Wed May 14 11:14:09 EDT 1997

