sub power {
    my $self=shift;
    if ($_[0]) {  
        my $power=shift;
        push @{$self->{POWERS}}, $power;
    } else {
        my $self=shift;
        my $num=1;
        foreach my $power ( @{$self->{POWERS}} ) {
        print "$num => $power\n";
        $num++;
        }
        print "\n";
    }
}