Why are you adding the socket to (just) $pexceptions? An incomming connection counts as a read. Since you didn't add the socket to $pread, the select won't wake up on an incomming connection. (A broken connection would be an example of an exception.) Add

$pread->add($sock);
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By the way, why did you make $pread, $pwrite, $read and $write singular? Like $pexceptions and $exceptions, they should be plural since they are lists.