I personally would not create a new table for each instance, but would instead have a static table that contains the key PARENTID or CHILDID depending on if you wanted the queues to be associated to the parent or child.

my $sth = $dbh->prepare(q{INSERT INTO TABLE QUEUE SET PARENTID=?, PAYL
+OAD=?});
$sth->execute($parentid, $payload) or die $dbh->errstr;
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Before each new instance of a parent is run, it should simply scan the table to see if there are any old records left over from a previous process with the same pid.