With my orginal post, I was thinking of the situation where you read a password from the user, check it in a database, and then get rid of it. Having it automatically self-destruct could be handy. Abigail pointed out that this is probably useful in far fewer situations than I thought it might be.

Also, it could force you to rely on the implementation of certain functions. For instance, your password-checker sub's first implementation might only need to fetch the password once, but a later implementation fetches it twice. Now you have to increment your self-destruct paramameter in a place that might be very distant from the password checker sub.

In any case, it was just a brainstorm. A thought placed Out There without any initial prejudice.