It would be helpful to know what unstable platform you're on or what unstable build of perl you're using.

Update: wow, then that shouldn't be happening imo; but, I have no further information on why. Is it the sun build of perl 5.8.8? What is $sig? Signals are kinda strange monsters (or can be depending on the implementation) and I can't help but wonder if $sig is getting deallocated lexically and then cleaned up again during global destruction or something vile like that.