Perl classes are based on packages, which are by nature open. So e.g. to add a foo() method to the CGI class you can do 
package main;

use strict;
use warnings;
use CGI;

package CGI;

sub foo {
    my $self = shift;
    return $self->p('foo');
} 

package main;

my $cgi = CGI->new;
print $cgi->foo() . "\n";

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In reply to Re: How could we "implement" Open Classes in Perl ? by Arunbear
in thread How could we "implement" Open Classes in Perl ? by Alien

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