Glad you asked this question, as it's something I'm going to have to grapple with in a few days. I'll watch this thread with interest to see if the answer to my question comes up :)

At the moment, how I'm planning to approach it (subject to revision by sibling monks) is

while (1) {
    open OFF, "off.txt";
    last if <OFF>;
    # all the code goes here
    sleep 5;
}
print "you turned me off!";
[download]

off.txt is a blank file. So then my script runs and runs and runs until I put something into off.txt, at which point the script breaks out of the loop.

As I say, that's how I'd do it... but I'd also ask how to do it before I did it that way. As you have.

§ George Sherston