Another thought would be to put a flag in your database that a waking process would check to see if there was another process already running.

That's a good thought. I implemented it five minutes, flat. This actually set my mind off on a tangent, and I created a DB-table to hold parameters for the program, as well, so that I can also track the most common invocations. Needed to make minor changes to the code (e.g. get parameters from DB via DBI instead from command-line), but it was smooth. Thanks for a great idea.