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package UNIVERSAL;
# UNIVERSAL should not contain any extra subs/methods beyond those
# that it exists to define. The use of Exporter below is a historical
# accident that should be fixed sometime.
require Exporter;
*import = \&Exporter::import;
@EXPORT_OK = qw(isa can);
1;
__END__
=head1 NAME
UNIVERSAL - base class for ALL classes (blessed references)
=head1 SYNOPSIS
$io = $fd->isa("IO::Handle");
$sub = $obj->can('print');
$yes = UNIVERSAL::isa($ref, "HASH");
=head1 DESCRIPTION
C<UNIVERSAL> is the base class which all bless references will inherit from,
see L<perlobj>
C<UNIVERSAL> provides the following methods
=over 4
=item isa ( TYPE )
C<isa> returns I<true> if C<REF> is blessed into package C<TYPE>
or inherits from package C<TYPE>.
C<isa> can be called as either a static or object method call.
=item can ( METHOD )
C<can> checks if the object has a method called C<METHOD>. If it does
then a reference to the sub is returned. If it does not then I<undef>
is returned.
C<can> can be called as either a static or object method call.
=item VERSION ( [ REQUIRE ] )
C<VERSION> will return the value of the variable C<$VERSION> in the
package the object is blessed into. If C<REQUIRE> is given then
it will do a comparison and die if the package version is not
greater than or equal to C<REQUIRE>.
C<VERSION> can be called as either a static or object method call.
=back
The C<isa> and C<can> methods can also be called as subroutines
=over 4
=item UNIVERSAL::isa ( VAL, TYPE )
C<isa> returns I<true> if the first argument is a reference and either
of the following statements is true.
=over 8
=item
C<VAL> is a blessed reference and is blessed into package C<TYPE>
or inherits from package C<TYPE>
=item
C<VAL> is a reference to a C<TYPE> of perl variable (er 'HASH')
=back
=item UNIVERSAL::can ( VAL, METHOD )
If C<VAL> is a blessed reference which has a method called C<METHOD>,
C<can> returns a reference to the subroutine. If C<VAL> is not
a blessed reference, or if it does not have a method C<METHOD>,
I<undef> is returned.
=back
These subroutines should I<not> be imported via S<C<use UNIVERSAL qw(...)>>.
If you want simple local access to them you can do
*isa = \&UNIVERSAL::isa;
to import isa into your package.
=cut
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