Whats more pertinent in perl I think is the code to find the _index_ of the first matching element in the array. A straight forward existance test is too easily outperformed by a hash. and its unusual in my experience that if you need to this more than once that pre-constructing the hash isnt possible. BTW, id be interested to see if you come up with the fastest technique. Suprisingly it is actually one of the longer solutions.