使ってないポートを取得する (Perl) ref: http://qiita.com/items/1018

file0.txt

#!/usr/bin/env perl
use strict;
use warnings;
use v5.14;
use IO::Socket::INET;sub empty_port () {
    my $sock = IO::Socket::INET->new(
        Prot   => 'tcp',
        Listen => 1,
        (($^O eq 'MSWin32') ? () : (ReuseAddr => 1)),
    );
    my $port = $sock->sockport;
    $sock->close;
    $port;
}say empty_port;