actually those timeout handling part in IO::Socket::INET module has been commented out. So there is no purpose to use the timeout().
In Authen::Radius module, then had ETIMEOUT error for indicating that timed out waiting for packet.
Comment on Re: what does timeout mean in IO::Socket::INET ?
Yes, it used by IO::Socket. But note that it use it only in connect and accept. So if you want timeout in sysread you should set socket option or better use IO::Select.