It is correct that currently memory is not returned to the system - however, it can be reused in the program, such as undefing varables (or resetting the to empty) to free memory for Perl to continue to use, thus limiting the process from expanding beyond neccesity.

As for unloading a module (accomplishing some thing similar to deleting variables), I'm going to go out on a limb and say that there isn't a way to do this. I can't find a mention while perusing the docs (but my doc perusing ability is notoriously bad. Without some explicit statement from the programmer, Perl can't know that your going to not use a module (or class) again, and I can't find mention of sucha mechanism. Additionally, there is little deep memory management in Perl (although we all wait for the less pragma) because Perl was designed (partially) to get those kinds of things out of the programmers hair.

Cheers,
Erik