mla,
please forgive my naive example but, i think iburrell and hossman are referring to something like below, where the actual lock is your pre-desctruct flag...

sub clean_up
{
    my $self = shift;
    if ( $self->{Lock} )
    {
        #
        #    the code to release the lock
        #

        $self->{Lock} = 0;
    }
}

sub DESTROY
{
    my $self = shift;
    $self->clean_up();
}
[download]