PERL does actually have a set of lockfile functions, but they didn't work very well on my system (I honestly followed the instructions, but I couldn't get it to lock reliably). Because of that, I ripped out the lockfile functions from Agora (an email-to-web gateway).

You can download these functions as lockfile.txt and then rename it to lockfile.pl. You add it to your PERL program with require "lockfile.pl" and use the SetLockFile() function below.

$FN = SetLockFile("/directory", "filename") - Creates a lockfile in the specified directory with "filename" as the lockfile's prefix. If there is a lock file already, it will wait and try again. It returns the full filename of the lock file. To remove the lock file, which you MUST do, call unlink($FN).