Heh... I just thought it was the profiler recursing a lot, but maybe you really do have an infinite loop there when the profiler is turned on.
The other thing you could do is try and debug it in the debugger, figure out what is going on that way. You might just spot something obvious. But I have to say, I don't have much experience with debugging global destruction. perldebug says:
Set the "inhibit_exit" option to 0 if you want
to be able to step off the end the script.
You may also need to set $finished to 0 if you
want to step through global destruction.
It sounds to me like the posix::_exit() workaround is good enough.