The problem, as noted by others, is that we can't see his code to make suggestions. Shrug. Can't help much there. He doesn't even say if he's using the Perl bioinformatics modules or if he's rolled his own.

In any case though, this is a problem that is begging for a parallel processing solution. In general, I'd recommend he break up the dataset and run it on all the machines in the lab. I doubt that there are many algorythmic improvements that can beat adding another 5 CPUs to the task.