package import dangers

[Ethan Furman]

Greetings!

I'm working on a package with multiple modules (and possibly packages), 
and I would like to do it correctly.  :)

I have read of references to possible issues regarding a module being 
imported (and run) more than once, but I haven't been able to find 
actual examples of such failing code.

My google search was fruitless (although still educational !-), so if 
anyone could point me in the right direction I would greatly appreciate it.

~Ethan~