Note that calling join on a thread waits for it to complete, so to prevent blocking you'll have to find a way to ensure that your thread terminates. Also, you might have to do some experimentation to determine which thread will get the signal.

I think you are better off using fork in this situation -it's going to be a lot simpler. Just keep track of the pids you create:

our @pids;
...
for my $db (keys %{$db_ds}) {
  ...
  my $pid = fork();
  if ($pid == 0) {
    exec(...);
  } else {
    push(@pids, $pid);
  }
}
[download]

and then call kill 9, @pids in your signal handler.

Finally, be sure to read perlthrtut -- it mentions some caveats about using signals and threads.