title: unloading code/modules
body: <p>I'm curious if there is any good way to unload a module after using it.  I have some cases where I need to use modules that bring in a lot of code, but they are used rarely (say as an admin tool), but I hesitate to use them because afterwards they'll presumably just waste memory that could be better used elsewhere. Is there any way to unload them, either explicitly or by allowing the system to do so when they haven't been used for a while?</p>