Ooow .... I like *that* idea :-) I've actually placed the '#undef malloc' at the very start of the C code in that script, and the script now runs fine.

I've had some success with doing that to avoid PerlAPI interfering in stuff that is none of its business.

But be careful. You can find yourself in the 'multiple C runtimes' trap passing pointers allocated by one to another to be freed with various possibilities of outcome.

BTW. You should also be very wary of passing pointers to memory allocated on the stack of one thread as the thread argument to another. I realise it was only demo code, but it's worth a heads up.