My best guess based on the scant information is that your main thread is ending without properly waiting for your other threads to be cleaned up. But it is nothing but a guess.

All the threads are joined. There are no active threads. No threads are detached. This code after the final join and before line 884 does not print anything:

foreach my $th(threads->list()) {
    print $th->tid()."\n";
}
[download]

I will ask this afternoon about sharing the code. This is urgent enough that I might get approval. Thanks for the help!