I'm reluctantly coming to the conclusion that I'll have to abandon the look-back array concept. Apparently, two-dimensional arrays in Perl are too difficult to actually use for someone at my level :(

I'll need at least three counters, though. The original array has data for up to a full year, and I have to start the comparison search over with each new day. So I'd need an overall original array counter, and the other two counters would reset when the day turns over.