Seconding what Corion said - mixing signals and threads is messy, and often unnecessary.

As for checking whether it's still running though - you can check thread state by testing "running":

    my @running = threads->list(threads::running);
    my @joinable = threads->list(threads::joinable);
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Or per thread:

foreach my $thr ( threads -> list ) { 
   print $thr. " is running\n" if $thr -> is_running(); 
   print $thr. " is joinable\n" if $thr -> is_joinable(); 
}
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