Rather than duplicating the whole parent class method, you can let it do most of the work: 
my $singleton;

sub new { 
    my $proto = shift;

    if ( !defined $singleton ) { 
        $singleton = $proto->SUPER::new( @_ );
    }

    return $singleton;
}

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In reply to Re^2: Making an Existing Class a Singleton by friedo
in thread Making an Existing Class a Singleton by agianni

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