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#!/usr/bin/perl

...
    sleep(3);
    waitpid(-1, WNOHANG);
}

$ ./check.pl 
process id: 4609
...
      06:29  4569  4569 Ss   bash
      00:12  4609  4609 S+    \_ /usr/bin/perl ./check.pl
      00:00  4624  4609 R+        \_ ps Tf -o etime,pid,pgrp,stat,cmd