perldoc perlipc says:
Sending a signal to a negative process ID means that you send the signal to the entire Unix process-group.
This code sends a hang-up signal to all processes in the current process group (and sets $SIG{HUP} to IGNORE so it doesn't kill itself):

     {
         local $SIG{HUP} = 'IGNORE';
         kill HUP => -$$;
         # snazzy writing of: kill('HUP', -$$)
     }
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Use this hint as a pointer. I haven't done much IPC stuff lately.
I am assuming that your script does not fork of other non-telnet processes that should not be killed.