sub os_port {
        foreach (@_) {
            $sock = new IO::Socket::INET(PeerAddr => $server,
                             PeerPort => $_,
                             Proto    => 'tcp');
            last if $sock;
        }
        $sock;
    }
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Subroutines defined at compile time have package scope so it makes little sense to define them inside a loop.    You will never get a new subroutine for each loop iteration.

        while (<$sock>) {
            $sock_string = $_;
            last;
        }
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Why not just:

        $sock_string = <$sock>;
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