Well if you're fortunate enough to be running this on a Unix system then you can re-schedule the priority of a process by being 'nice' to the process. If you have permissions you can use the renice command (man renice(8)) which should lower it's CPU usage significantly (assuming you give it a positive value). This isn't part of perl's functionality, so you'll probably have to run the command through system() or something of that ilk, as I don't think there's a CPAN module for it (now would be a good time to write one though ;o)
HTH

broquaint