Great reply, tilly. Thanks very much. I have already put into action the hash of arrays solution and I shall look at implementing hash of hashes when I get my head around it. I was also pleased that you answered the original question tho' I do understand why I shouldn't use it in this case.

I must confess that though I have read up on this sort of thing in the past and it all seemed to make sense, it didn't really click back then. Now that I have an implementation of my own to do I feel I can really make some progress with it. Cheers