sub get_pairs {
    my %invalids = ();
    my @valids = ();
    for $number (@_) {
        for $id (@{$contains{$number}}) {
            $invalids{$id} = 1;
        }
    }
    for ($id=0; $id < $#items; $id++) {
        push @valids, $items[$id];
    }
    return @valids;
}

@all_matches = get_pairs(2,3,4)