q -> end is something that a newer version of the Thread::Queue library supports - it's why I didn't use it initially either. And worked around it by some sort of fiddle with pending, semaphores or queuing a load of 'exit' codes. As an alternative, I might offer 'thread->kill'. If you override 'SIGTERM' (which is normally an 'unmaskable' interrupt) you can send 'SIGTERM' to your thread to force it to exit.) E.g.:

#add to thread:
$SIG{'TERM'} = sub { threads->exit(); };


## just before the 'join' add:
$thr -> kill ( "SIGTERM" );
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This isn't a 'real' SIGTERM as PERL can't trap those - but it's a good way of getting a thread to preemptively terminate. (Although, I'd note that _because_ it's not a 'proper' SIGTERM, it also might be delayed until the current function call has finished.

I would normally start the threads first, but dislike doing it if it might 'die' on that file open. There are neater ways of doing it, but I thought to err on the side of brevity.