yes, by the results I was seeing, I had a feeling that that was what was happening, ie, they weren't even going to disk. I was getting caught in the paradigm that only variables resided in memory.

Another paradigm that I am wondering if it is fallacious is that calling a system command is more expensive than using a module. Is there really a (significant) difference between forking a process and executing code that is written in from a module? If there is a slight cost to forking, it doesn't seem like it would be that significant. Some one enlighten me.

Anyway, looking at the results of my tests, it is hard to convince me that there is anything to be gained by using Algorithm::Diff, as far as speed goes. Portability, perhaps, as some have pointed out.