I would like to know more about what your Perl task is going to do?

In general, for task that runs say once per hour and runs for a few seconds, cron is the way to go. You get a "new instance" and memory "leaks" are not as big of a concern. Very long lived processes require a lot more care.

If you have a program that "watches" a directory for new files, there are ways to do this under unix on an event driven basis.

Can you provide more info? Your question is so general that I don't know how to proceed.