Thanks for the example! I'll check it out.

I'm sorry I provided the wrong link. The code I wrote comes from this code taken directly from the examples directory of the threads CPAN distro by JDHEDDEN. It's called pool_reuse.pl

The block by block comparison of files which you proposed is actually part of my next approach. I may be able to forgo the need to digest the file content altogether and get a real speed boost by only reading as many bytes from a file as I need to in order to tell that it's different. Much less IO required.