If you're using Perl threads, you shouldn't have to worry about whether it is actually implemented using processes or real threads™. That's why they're "Perl threads".

Having said that, to my knowledge, Linux is the only system where you can actually think of threads as processes, as having seperate program id's (pid's, $$). This allows modules as Thread::Signal to function in that environment. Win32 only knows about real threads and mimics fork() using threads. Other *nixes are somewhere inbetween. Some can fork() and have real threads (Solaris seems to fall in that group). But e.g. on Mac OS X (and presumably other BSD's), threads look as seperate processes, but can not be signalled.

...never-ending sub (ie it's got a while (1) loop)m how can I stop it nevertheless?

Use a shared variable in the while. So:

while (1) {
[download]

while ($sharedvar) {
[download]

In that respect, you might also want to have a look at Thread::Queue::Monitored and/or Thread::Conveyor::Monitored.

Hope this helps.

Liz

Update:
I forgot one other way to do this. This will only work if you are running under Linux for now. Use Thread::Signal to activate a handler that will do a Thread::Exit. No nice cleanup that way, but definitely effective ;-)