Without sight of the whole program, this is impossible to answer. Any speculations would be, exactly that: speculation.

Along with posting your script (preferably cut down to the minimum that demonstrates the error), you will also need to give a few details of your environment.

1. Which version of perl?
2. What OS/version?
3. What dependancies/versions?

A few preemptive strikes are possible.

• If you're using pThreads--don't.
• If you're using iThreads and a version of perl earlier than 5.8.4--upgrade.
• If you're sharing objects between threads--stop!

I'll try to be more helpful once you supply some more information.

For the record, the iThreads API does not provide for any mechanism for killing threads. It is possible, with caveats, to do this under Win32.

I am not aware of a mechanism for doing under other OSs, though that's isn't saying much, as I am very unfamiliar with other OSs :)