Mixing signal handling and threads is unwise. The problem is that you have no control over which thread will receive the signal. If 2 threads disagree on how to handle the signal, you get inconsistent behaviour.
To get unsafe signal handling in Perl, you just need to set the environment variable PERL_SIGNALS to the value "unsafe" before you call Perl. Unsafe signal handling is important when you have long-running opcodes that might block the handling of a signal. A perfect example of such an opcode is calling out to a C library. Think a long-running database handler. If you are using safe signals, that query cannot be interrupted. Your problem doesn't "smell" like an unsafe signals issue, but now you know how to do it if you want to experiment.
