mirror of
https://git.savannah.gnu.org/git/parallel.git
synced 2024-12-23 13:17:54 +00:00
266 lines
6.8 KiB
Perl
266 lines
6.8 KiB
Perl
package base;
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use strict 'vars';
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use vars qw($VERSION);
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$VERSION = '2.16';
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$VERSION = eval $VERSION;
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# constant.pm is slow
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sub SUCCESS () { 1 }
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sub PUBLIC () { 2**0 }
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sub PRIVATE () { 2**1 }
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sub INHERITED () { 2**2 }
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sub PROTECTED () { 2**3 }
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my $Fattr = \%fields::attr;
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sub has_fields {
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my($base) = shift;
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my $fglob = ${"$base\::"}{FIELDS};
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return( ($fglob && 'GLOB' eq ref($fglob) && *$fglob{HASH}) ? 1 : 0 );
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}
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sub has_version {
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my($base) = shift;
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my $vglob = ${$base.'::'}{VERSION};
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return( ($vglob && *$vglob{SCALAR}) ? 1 : 0 );
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}
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sub has_attr {
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my($proto) = shift;
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my($class) = ref $proto || $proto;
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return exists $Fattr->{$class};
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}
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sub get_attr {
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$Fattr->{$_[0]} = [1] unless $Fattr->{$_[0]};
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return $Fattr->{$_[0]};
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}
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if ($] < 5.009) {
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*get_fields = sub {
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# Shut up a possible typo warning.
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() = \%{$_[0].'::FIELDS'};
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my $f = \%{$_[0].'::FIELDS'};
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# should be centralized in fields? perhaps
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# fields::mk_FIELDS_be_OK. Peh. As long as %{ $package . '::FIELDS' }
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# is used here anyway, it doesn't matter.
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bless $f, 'pseudohash' if (ref($f) ne 'pseudohash');
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return $f;
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}
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}
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else {
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*get_fields = sub {
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# Shut up a possible typo warning.
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() = \%{$_[0].'::FIELDS'};
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return \%{$_[0].'::FIELDS'};
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}
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}
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sub import {
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my $class = shift;
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return SUCCESS unless @_;
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# List of base classes from which we will inherit %FIELDS.
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my $fields_base;
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my $inheritor = caller(0);
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my @isa_classes;
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my @bases;
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foreach my $base (@_) {
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if ( $inheritor eq $base ) {
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warn "Class '$inheritor' tried to inherit from itself\n";
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}
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next if grep $_->isa($base), ($inheritor, @bases);
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if (has_version($base)) {
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${$base.'::VERSION'} = '-1, set by base.pm'
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unless defined ${$base.'::VERSION'};
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}
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else {
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my $sigdie;
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{
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local $SIG{__DIE__};
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eval "require $base";
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# Only ignore "Can't locate" errors from our eval require.
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# Other fatal errors (syntax etc) must be reported.
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die if $@ && $@ !~ /^Can't locate .*? at \(eval /;
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unless (%{"$base\::"}) {
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require Carp;
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local $" = " ";
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Carp::croak(<<ERROR);
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Base class package "$base" is empty.
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(Perhaps you need to 'use' the module which defines that package first,
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or make that module available in \@INC (\@INC contains: @INC).
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ERROR
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}
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$sigdie = $SIG{__DIE__} || undef;
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}
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# Make sure a global $SIG{__DIE__} makes it out of the localization.
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$SIG{__DIE__} = $sigdie if defined $sigdie;
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${$base.'::VERSION'} = "-1, set by base.pm"
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unless defined ${$base.'::VERSION'};
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}
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push @bases, $base;
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if ( has_fields($base) || has_attr($base) ) {
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# No multiple fields inheritance *suck*
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if ($fields_base) {
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require Carp;
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Carp::croak("Can't multiply inherit fields");
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} else {
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$fields_base = $base;
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}
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}
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}
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# Save this until the end so it's all or nothing if the above loop croaks.
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push @{"$inheritor\::ISA"}, @isa_classes;
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push @{"$inheritor\::ISA"}, @bases;
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if( defined $fields_base ) {
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inherit_fields($inheritor, $fields_base);
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}
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}
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sub inherit_fields {
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my($derived, $base) = @_;
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return SUCCESS unless $base;
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my $battr = get_attr($base);
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my $dattr = get_attr($derived);
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my $dfields = get_fields($derived);
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my $bfields = get_fields($base);
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$dattr->[0] = @$battr;
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if( keys %$dfields ) {
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warn <<"END";
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$derived is inheriting from $base but already has its own fields!
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This will cause problems. Be sure you use base BEFORE declaring fields.
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END
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}
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# Iterate through the base's fields adding all the non-private
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# ones to the derived class. Hang on to the original attribute
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# (Public, Private, etc...) and add Inherited.
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# This is all too complicated to do efficiently with add_fields().
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while (my($k,$v) = each %$bfields) {
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my $fno;
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if ($fno = $dfields->{$k} and $fno != $v) {
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require Carp;
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Carp::croak ("Inherited fields can't override existing fields");
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}
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if( $battr->[$v] & PRIVATE ) {
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$dattr->[$v] = PRIVATE | INHERITED;
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}
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else {
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$dattr->[$v] = INHERITED | $battr->[$v];
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$dfields->{$k} = $v;
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}
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}
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foreach my $idx (1..$#{$battr}) {
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next if defined $dattr->[$idx];
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$dattr->[$idx] = $battr->[$idx] & INHERITED;
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}
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}
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1;
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__END__
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=head1 NAME
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base - Establish an ISA relationship with base classes at compile time
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=head1 SYNOPSIS
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package Baz;
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use base qw(Foo Bar);
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=head1 DESCRIPTION
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Unless you are using the C<fields> pragma, consider this module discouraged
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in favor of the lighter-weight C<parent>.
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Allows you to both load one or more modules, while setting up inheritance from
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those modules at the same time. Roughly similar in effect to
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package Baz;
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BEGIN {
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require Foo;
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require Bar;
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push @ISA, qw(Foo Bar);
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}
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C<base> employs some heuristics to determine if a module has already been
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loaded, if it has it doesn't try again. If C<base> tries to C<require> the
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module it will not die if it cannot find the module's file, but will die on any
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other error. After all this, should your base class be empty, containing no
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symbols, it will die. This is useful for inheriting from classes in the same
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file as yourself, like so:
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package Foo;
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sub exclaim { "I can have such a thing?!" }
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package Bar;
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use base "Foo";
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If $VERSION is not detected even after loading it, <base> will define $VERSION
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in the base package, setting it to the string C<-1, set by base.pm>.
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C<base> will also initialize the fields if one of the base classes has it.
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Multiple inheritance of fields is B<NOT> supported, if two or more base classes
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each have inheritable fields the 'base' pragma will croak. See L<fields>,
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L<public> and L<protected> for a description of this feature.
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The base class' C<import> method is B<not> called.
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=head1 DIAGNOSTICS
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=over 4
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=item Base class package "%s" is empty.
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base.pm was unable to require the base package, because it was not
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found in your path.
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=item Class 'Foo' tried to inherit from itself
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Attempting to inherit from yourself generates a warning.
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package Foo;
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use base 'Foo';
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=back
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=head1 HISTORY
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This module was introduced with Perl 5.004_04.
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=head1 CAVEATS
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Due to the limitations of the implementation, you must use
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base I<before> you declare any of your own fields.
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=head1 SEE ALSO
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L<fields>
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=cut
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