in reply to IO::Socket what's this doing?

From reading the code it appears you are on a *nix system.

If you are curious about the different signals you can send/receive you can type

kill -l
to get a list of all the commands that can be sent to a process (along with their numerical equivs).

--
I used to drive a Heisenbergmobile, but every time I looked at the speedometer, I got lost.