Thanks for the link. I am sure I can use that module in a script I wrote at work, but not here. Here, I may be comparing two large tables and finding one or two rows that differ. I can't put it all in memory, especially not in seen-hashes. I need to be able to suck rows one at a time from MySQL, in sorted order, and have Perl know when a row is missing from one table because one row is "greater than" or "less than" the other.

I've seen the term XY but not seen a definition. What does it mean?