I successfully embedded perl in foxpro. When you unload the .dll foxpro segfaults. I then rewrote the app to not use perl because foxpro isn't stable enough to handle unloading perl...

I also maintain a hideous and evil Sendmail::Milter application. Perl threads just don't seem to have the juice required to make that work. They run pretty solid (as long as you don't exit and get those mysterious memory leak messages), but you can't use signals in a threaded app -- so you don't get to use timeouts for things that block. Perhaps I just suck at perl threads... In any case, I'm re-writing that legacy app to not be a sendmail milter (which requires threads).

In short, due to limitations with sendmail and foxpro, I find perl doesn't fit well in them.