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Name	Size	Permission	Date
Algorithm	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
App	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Archive	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Array	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Attribute	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
B	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
CORE	[ DIR ]	drwxrwxrwx	2024-07-26 17:42
CPAN	[ DIR ]	drwxrwxrwx	2024-07-26 17:42
Capture	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Carp	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Class	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Compress	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Config	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
DBM_Filter	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Data	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Devel	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Digest	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Encode	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Exporter	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
ExtUtils	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
File	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Filter	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Getopt	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
HTML	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
HTTP	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Hash	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
I18N	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
IO	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
IPC	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
JSON	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
List	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Locale	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
MIME	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
MRO	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Math	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Memoize	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Module	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Net	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Params	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Parse	[ DIR ]	drwxrwxrwx	2024-07-26 17:38
Perl	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
PerlIO	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Pod	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Regexp	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Scalar	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Search	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Software	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
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Sys	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
TAP	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Term	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Test	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Test2	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Text	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Thread	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Tie	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Time	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Try	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
URI	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Unicode	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
User	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
Win32API	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
auto	[ DIR ]	drwxrwxrwx	2024-07-26 17:38
autodie	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
encoding	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
overload	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
pods	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
threads	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
unicore	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
version	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
warnings	[ DIR ]	drwxrwxrwx	2024-07-26 17:40
.packlist	90.29 KB	-rw-rw-rw-	2021-01-24 16:08
AnyDBM_File.pm	2.56 KB	-rw-rw-rw-	2020-12-18 11:58
AutoLoader.pm	15.43 KB	-rw-rw-rw-	2020-12-18 11:57
AutoSplit.pm	19.18 KB	-rw-rw-rw-	2020-12-18 11:57
B.pm	28.78 KB	-rw-rw-rw-	2020-12-18 12:04
Benchmark.pm	30.3 KB	-rw-rw-rw-	2020-12-18 11:58
CORE.pod	3.11 KB	-rw-rw-rw-	2020-12-18 11:58
CPAN.pm	142.98 KB	-rw-rw-rw-	2020-06-13 08:47
Carp.pm	35.12 KB	-rw-rw-rw-	2020-12-18 12:04
Config.pm	3.29 KB	-rw-rw-rw-	2024-07-26 17:42
Config.pod	258.26 KB	-rw-rw-rw-	2021-01-24 16:01
Config_git.pl	421 B	-rw-rw-rw-	2021-01-24 16:01
Config_heavy.pl	37.27 KB	-rw-rw-rw-	2023-11-19 11:41
Cwd.pm	21.43 KB	-rw-rw-rw-	2020-12-18 12:04
DB.pm	18.48 KB	-rw-rw-rw-	2020-12-18 11:58
DBM_Filter.pm	14.05 KB	-rw-rw-rw-	2020-12-18 11:58
Digest.pm	10.96 KB	-rw-rw-rw-	2020-10-13 23:59
DirHandle.pm	2.04 KB	-rw-rw-rw-	2020-12-18 11:58
Dumpvalue.pm	17.25 KB	-rw-rw-rw-	2020-12-18 11:58
DynaLoader.pm	25.4 KB	-rw-rw-rw-	2021-01-24 16:01
Encode.pm	31.33 KB	-rw-rw-rw-	2020-12-02 03:28
English.pm	4.65 KB	-rw-rw-rw-	2020-12-18 11:58
Env.pm	5.39 KB	-rw-rw-rw-	2020-12-18 12:04
Errno.pm	92.68 KB	-rw-rw-rw-	2021-01-24 16:07
Exporter.pm	18.36 KB	-rw-rw-rw-	2020-12-18 12:04
Fatal.pm	57.7 KB	-rw-rw-rw-	2021-01-22 19:03
Fcntl.pm	3.95 KB	-rw-rw-rw-	2020-12-18 12:04
FileCache.pm	5.42 KB	-rw-rw-rw-	2020-12-18 11:58
FileHandle.pm	6.63 KB	-rw-rw-rw-	2020-12-18 11:58
FindBin.pm	4.54 KB	-rw-rw-rw-	2020-12-11 21:08
GDBM_File.pm	2.03 KB	-rw-rw-rw-	2020-12-18 11:58
IO.pm	1.42 KB	-rw-rw-rw-	2021-01-05 00:24
Internals.pod	2.51 KB	-rw-rw-rw-	2020-12-18 11:58
Memoize.pm	35.34 KB	-rw-rw-rw-	2020-12-18 11:58
NDBM_File.pm	3.01 KB	-rw-rw-rw-	2020-12-18 11:58
NEXT.pm	18.54 KB	-rw-rw-rw-	2020-12-18 11:58
O.pm	4.19 KB	-rw-rw-rw-	2020-12-18 11:58
ODBM_File.pm	2.9 KB	-rw-rw-rw-	2020-12-18 12:04
Opcode.pm	15.85 KB	-rw-rw-rw-	2021-01-09 14:15
POSIX.pm	19.87 KB	-rw-rw-rw-	2020-12-18 12:04
POSIX.pod	78.81 KB	-rw-rw-rw-	2020-12-18 12:04
PerlIO.pm	14.1 KB	-rw-rw-rw-	2020-12-18 11:58
SDBM_File.pm	3.72 KB	-rw-rw-rw-	2020-12-18 11:58
Safe.pm	24.77 KB	-rw-rw-rw-	2021-01-09 14:15
SelectSaver.pm	1.05 KB	-rw-rw-rw-	2020-12-18 11:58
SelfLoader.pm	17.27 KB	-rw-rw-rw-	2020-12-18 11:58
Socket.pm	36.16 KB	-rw-rw-rw-	2021-01-05 17:48
Storable.pm	48.75 KB	-rw-rw-rw-	2020-12-18 12:04
Symbol.pm	4.69 KB	-rw-rw-rw-	2020-12-18 12:04
Test.pm	29.34 KB	-rw-rw-rw-	2020-12-18 11:58
Test2.pm	6.24 KB	-rw-rw-rw-	2020-10-22 07:10
Thread.pm	8.09 KB	-rw-rw-rw-	2020-12-18 11:58
UNIVERSAL.pm	6.44 KB	-rw-rw-rw-	2020-12-18 11:58
URI.pm	33.95 KB	-rw-rw-rw-	2021-01-14 18:01
Win32.pm	57.28 KB	-rw-rw-rw-	2020-03-28 07:37
Win32CORE.pm	1.27 KB	-rw-rw-rw-	2020-12-18 11:58
XSLoader.pm	11.37 KB	-rw-rw-rw-	2021-01-24 16:07
_charnames.pm	33.35 KB	-rw-rw-rw-	2020-12-18 11:58
attributes.pm	15.97 KB	-rw-rw-rw-	2020-12-18 11:58
autodie.pm	12.14 KB	-rw-rw-rw-	2021-01-22 19:03
autouse.pm	4.14 KB	-rw-rw-rw-	2020-12-18 11:58
base.pm	10.7 KB	-rw-rw-rw-	2020-12-18 11:58
bigint.pm	22.85 KB	-rw-rw-rw-	2020-12-18 11:58
bignum.pm	20.64 KB	-rw-rw-rw-	2020-12-18 11:58
bigrat.pm	15.78 KB	-rw-rw-rw-	2020-12-18 11:58
blib.pm	2.01 KB	-rw-rw-rw-	2020-12-18 11:58
bytes.pm	3.65 KB	-rw-rw-rw-	2020-12-18 12:04
bytes_heavy.pl	758 B	-rw-rw-rw-	2020-12-18 11:58
charnames.pm	20.44 KB	-rw-rw-rw-	2020-12-18 11:58
constant.pm	14.38 KB	-rw-rw-rw-	2020-12-18 11:58
cpanfile-faq.pod	4.39 KB	-rw-rw-rw-	2018-04-26 13:07
cpanfile.pod	3.39 KB	-rw-rw-rw-	2018-04-26 13:07
deprecate.pm	4.5 KB	-rw-rw-rw-	2020-12-18 11:58
diagnostics.pm	18.85 KB	-rw-rw-rw-	2020-12-18 11:58
dumpvar.pl	15.19 KB	-rw-rw-rw-	2020-12-18 11:58
encoding.pm	22.41 KB	-rw-rw-rw-	2020-12-18 11:57
experimental.pm	7.39 KB	-rw-rw-rw-	2020-05-05 00:34
feature.pm	18.56 KB	-rw-rw-rw-	2020-12-18 12:04
fields.pm	9.25 KB	-rw-rw-rw-	2020-12-18 11:58
filetest.pm	3.91 KB	-rw-rw-rw-	2020-12-18 11:58
if.pm	3.53 KB	-rw-rw-rw-	2020-12-18 12:04
integer.pm	3.18 KB	-rw-rw-rw-	2020-12-18 11:58
less.pm	3.13 KB	-rw-rw-rw-	2020-12-18 11:58
lib.pm	6.2 KB	-rw-rw-rw-	2021-01-24 16:01
locale.pm	4.74 KB	-rw-rw-rw-	2020-12-18 12:04
meta_notation.pm	2.07 KB	-rw-rw-rw-	2020-12-18 11:58
mro.pm	9.66 KB	-rw-rw-rw-	2020-12-18 12:04
newgetopt.pl	2.15 KB	-rw-rw-rw-	2010-07-09 16:26
ok.pm	967 B	-rw-rw-rw-	2020-10-22 07:10
open.pm	8.31 KB	-rw-rw-rw-	2020-12-18 11:58
ops.pm	997 B	-rw-rw-rw-	2020-12-18 11:58
overload.pm	52.05 KB	-rw-rw-rw-	2020-12-18 12:04
overloading.pm	1.77 KB	-rw-rw-rw-	2020-12-18 11:58
parent.pm	2.64 KB	-rw-rw-rw-	2020-12-18 11:58
perl5db.pl	309.69 KB	-rw-rw-rw-	2020-12-18 12:04
perlfaq.pm	77 B	-rw-rw-rw-	2020-11-07 23:02
perlfaq.pod	22.19 KB	-rw-rw-rw-	2020-11-07 23:02
perlfaq1.pod	14.09 KB	-rw-rw-rw-	2020-11-07 23:02
perlfaq2.pod	9.16 KB	-rw-rw-rw-	2020-11-07 23:02
perlfaq3.pod	36.72 KB	-rw-rw-rw-	2020-11-07 23:02
perlfaq4.pod	86.87 KB	-rw-rw-rw-	2020-11-07 23:02
perlfaq5.pod	54.21 KB	-rw-rw-rw-	2020-11-07 23:02
perlfaq6.pod	38.61 KB	-rw-rw-rw-	2020-11-07 23:02
perlfaq7.pod	36.93 KB	-rw-rw-rw-	2020-11-07 23:02
perlfaq8.pod	48.77 KB	-rw-rw-rw-	2020-11-07 23:02
perlfaq9.pod	14.86 KB	-rw-rw-rw-	2020-11-07 23:02
perlglossary.pod	134.02 KB	-rw-rw-rw-	2020-11-07 23:02
perllocal.pod	115.37 KB	-rw-rw-rw-	2021-01-24 18:08
re.pm	24.8 KB	-rw-rw-rw-	2020-12-18 12:04
sigtrap.pm	8.53 KB	-rw-rw-rw-	2020-12-18 11:58
sort.pm	3.82 KB	-rw-rw-rw-	2020-12-18 11:58
strict.pm	4.63 KB	-rw-rw-rw-	2020-12-18 12:04
subs.pm	901 B	-rw-rw-rw-	2020-12-18 12:04
threads.pm	37.06 KB	-rw-rw-rw-	2020-12-18 12:04
utf8.pm	10.18 KB	-rw-rw-rw-	2020-12-18 12:04
vars.pm	2.4 KB	-rw-rw-rw-	2020-12-18 11:58
version.pm	3.47 KB	-rw-rw-rw-	2020-09-22 22:16
version.pod	9.6 KB	-rw-rw-rw-	2020-07-31 20:44
vmsish.pm	4.21 KB	-rw-rw-rw-	2020-12-18 11:58
warnings.pm	49.35 KB	-rw-rw-rw-	2020-12-18 12:04

Rename

use 5.008;
package base;

use strict 'vars';
our $VERSION = '2.27';
$VERSION =~ tr/_//d;

# simplest way to avoid indexing of the package: no package statement
sub base::__inc::unhook { @INC = grep !(ref eq 'CODE' && $_ == $_[0]), @INC }
# instance is blessed array of coderefs to be removed from @INC at scope exit
sub base::__inc::scope_guard::DESTROY { base::__inc::unhook $_ for @{$_[0]} }

# constant.pm is slow
sub SUCCESS () { 1 }

sub PUBLIC     () { 2**0  }
sub PRIVATE    () { 2**1  }
sub INHERITED  () { 2**2  }
sub PROTECTED  () { 2**3  }

my $Fattr = \%fields::attr;

sub has_fields {
    my($base) = shift;
    my $fglob = ${"$base\::"}{FIELDS};
    return( ($fglob && 'GLOB' eq ref($fglob) && *$fglob{HASH}) ? 1 : 0 );
}

sub has_attr {
    my($proto) = shift;
    my($class) = ref $proto || $proto;
    return exists $Fattr->{$class};
}

sub get_attr {
    $Fattr->{$_[0]} = [1] unless $Fattr->{$_[0]};
    return $Fattr->{$_[0]};
}

if ($] < 5.009) {
    *get_fields = sub {
        # Shut up a possible typo warning.
        () = \%{$_[0].'::FIELDS'};
        my $f = \%{$_[0].'::FIELDS'};

# should be centralized in fields? perhaps
        # fields::mk_FIELDS_be_OK. Peh. As long as %{ $package . '::FIELDS' }
        # is used here anyway, it doesn't matter.
        bless $f, 'pseudohash' if (ref($f) ne 'pseudohash');

return $f;
    }
}
else {
    *get_fields = sub {
        # Shut up a possible typo warning.
        () = \%{$_[0].'::FIELDS'};
        return \%{$_[0].'::FIELDS'};
    }
}

if ($] < 5.008) {
    *_module_to_filename = sub {
        (my $fn = $_[0]) =~ s!::!/!g;
        $fn .= '.pm';
        return $fn;
    }
}
else {
    *_module_to_filename = sub {
        (my $fn = $_[0]) =~ s!::!/!g;
        $fn .= '.pm';
        utf8::encode($fn);
        return $fn;
    }
}

sub import {
    my $class = shift;

return SUCCESS unless @_;

# List of base classes from which we will inherit %FIELDS.
    my $fields_base;

my $inheritor = caller(0);

my @bases;
    foreach my $base (@_) {
        if ( $inheritor eq $base ) {
            warn "Class '$inheritor' tried to inherit from itself\n";
        }

next if grep $_->isa($base), ($inheritor, @bases);

# Following blocks help isolate $SIG{__DIE__} and @INC changes
        {
            my $sigdie;
            {
                local $SIG{__DIE__};
                my $fn = _module_to_filename($base);
                my $dot_hidden;
                eval {
                    my $guard;
                    if ($INC[-1] eq '.' && %{"$base\::"}) {
                        # So:  the package already exists   => this an optional load
                        # And: there is a dot at the end of @INC  => we want to hide it
                        # However: we only want to hide it during our *own* require()
                        # (i.e. without affecting nested require()s).
                        # So we add a hook to @INC whose job is to hide the dot, but which
                        # first checks checks the callstack depth, because within nested
                        # require()s the callstack is deeper.
                        # Since CORE::GLOBAL::require makes it unknowable in advance what
                        # the exact relevant callstack depth will be, we have to record it
                        # inside a hook. So we put another hook just for that at the front
                        # of @INC, where it's guaranteed to run -- immediately.
                        # The dot-hiding hook does its job by sitting directly in front of
                        # the dot and removing itself from @INC when reached. This causes
                        # the dot to move up one index in @INC, causing the loop inside
                        # pp_require() to skip it.
                        # Loaded coded may disturb this precise arrangement, but that's OK
                        # because the hook is inert by that time. It is only active during
                        # the top-level require(), when @INC is in our control. The only
                        # possible gotcha is if other hooks already in @INC modify @INC in
                        # some way during that initial require().
                        # Note that this jiggery hookery works just fine recursively: if
                        # a module loaded via base.pm uses base.pm itself, there will be
                        # one pair of hooks in @INC per base::import call frame, but the
                        # pairs from different nestings do not interfere with each other.
                        my $lvl;
                        unshift @INC,        sub { return if defined $lvl; 1 while defined caller ++$lvl; () };
                        splice  @INC, -1, 0, sub { return if defined caller $lvl; ++$dot_hidden, &base::__inc::unhook; () };
                        $guard = bless [ @INC[0,-2] ], 'base::__inc::scope_guard';
                    }
                    require $fn
                };
                if ($dot_hidden && (my @fn = grep -e && !( -d _ || -b _ ), $fn.'c', $fn)) {
                    require Carp;
                    Carp::croak(<<ERROR);
Base class package "$base" is not empty but "$fn[0]" exists in the current directory.
    To help avoid security issues, base.pm now refuses to load optional modules
    from the current working directory when it is the last entry in \@INC.
    If your software worked on previous versions of Perl, the best solution
    is to use FindBin to detect the path properly and to add that path to
    \@INC.  As a last resort, you can re-enable looking in the current working
    directory by adding "use lib '.'" to your code.
ERROR
                }
                # Only ignore "Can't locate" errors from our eval require.
                # Other fatal errors (syntax etc) must be reported.
                #
                # changing the check here is fragile - if the check
                # here isn't catching every error you want, you should
                # probably be using parent.pm, which doesn't try to
                # guess whether require is needed or failed,
                # see [perl #118561]
                die if $@ && $@ !~ /^Can't locate \Q$fn\E .*? at .* line [0-9]+(?:, <[^>]*> (?:line|chunk) [0-9]+)?\.\n\z/s
                          || $@ =~ /Compilation failed in require at .* line [0-9]+(?:, <[^>]*> (?:line|chunk) [0-9]+)?\.\n\z/;
                unless (%{"$base\::"}) {
                    require Carp;
                    local $" = " ";
                    Carp::croak(<<ERROR);
Base class package "$base" is empty.
    (Perhaps you need to 'use' the module which defines that package first,
    or make that module available in \@INC (\@INC contains: @INC).
ERROR
                }
                $sigdie = $SIG{__DIE__} || undef;
            }
            # Make sure a global $SIG{__DIE__} makes it out of the localization.
            $SIG{__DIE__} = $sigdie if defined $sigdie;
        }
        push @bases, $base;

if ( has_fields($base) || has_attr($base) ) {
            # No multiple fields inheritance *suck*
            if ($fields_base) {
                require Carp;
                Carp::croak("Can't multiply inherit fields");
            } else {
                $fields_base = $base;
            }
        }
    }
    # Save this until the end so it's all or nothing if the above loop croaks.
    push @{"$inheritor\::ISA"}, @bases;

if( defined $fields_base ) {
        inherit_fields($inheritor, $fields_base);
    }
}

sub inherit_fields {
    my($derived, $base) = @_;

return SUCCESS unless $base;

my $battr = get_attr($base);
    my $dattr = get_attr($derived);
    my $dfields = get_fields($derived);
    my $bfields = get_fields($base);

$dattr->[0] = @$battr;

if( keys %$dfields ) {
        warn <<"END";
$derived is inheriting from $base but already has its own fields!
This will cause problems.  Be sure you use base BEFORE declaring fields.
END

}

# Iterate through the base's fields adding all the non-private
    # ones to the derived class.  Hang on to the original attribute
    # (Public, Private, etc...) and add Inherited.
    # This is all too complicated to do efficiently with add_fields().
    while (my($k,$v) = each %$bfields) {
        my $fno;
        if ($fno = $dfields->{$k} and $fno != $v) {
            require Carp;
            Carp::croak ("Inherited fields can't override existing fields");
        }

if( $battr->[$v] & PRIVATE ) {
            $dattr->[$v] = PRIVATE | INHERITED;
        }
        else {
            $dattr->[$v] = INHERITED | $battr->[$v];
            $dfields->{$k} = $v;
        }
    }

foreach my $idx (1..$#{$battr}) {
        next if defined $dattr->[$idx];
        $dattr->[$idx] = $battr->[$idx] & INHERITED;
    }
}

__END__

=head1 NAME

base - Establish an ISA relationship with base classes at compile time

=head1 SYNOPSIS

package Baz;
    use base qw(Foo Bar);

=head1 DESCRIPTION

Unless you are using the C<fields> pragma, consider this module discouraged
in favor of the lighter-weight C<parent>.

Allows you to both load one or more modules, while setting up inheritance from
those modules at the same time.  Roughly similar in effect to

package Baz;
    BEGIN {
        require Foo;
        require Bar;
        push @ISA, qw(Foo Bar);
    }

When C<base> tries to C<require> a module, it will not die if it cannot find
the module's file, but will die on any other error.  After all this, should
your base class be empty, containing no symbols, C<base> will die. This is
useful for inheriting from classes in the same file as yourself but where
the filename does not match the base module name, like so:

# in Bar.pm
        package Foo;
        sub exclaim { "I can have such a thing?!" }

package Bar;
        use base "Foo";

There is no F<Foo.pm>, but because C<Foo> defines a symbol (the C<exclaim>
subroutine), C<base> will not die when the C<require> fails to load F<Foo.pm>.

C<base> will also initialize the fields if one of the base classes has it.
Multiple inheritance of fields is B<NOT> supported, if two or more base classes
each have inheritable fields the 'base' pragma will croak. See L<fields>
for a description of this feature.

The base class' C<import> method is B<not> called.

=head1 DIAGNOSTICS

=over 4

=item Base class package "%s" is empty.

base.pm was unable to require the base package, because it was not
found in your path.

=item Class 'Foo' tried to inherit from itself

Attempting to inherit from yourself generates a warning.

package Foo;
    use base 'Foo';

=back

=head1 HISTORY

This module was introduced with Perl 5.004_04.

=head1 CAVEATS

Due to the limitations of the implementation, you must use
base I<before> you declare any of your own fields.

=head1 SEE ALSO

L<fields>

=cut