Finds hostname aliases for IP's and vice versa.
Not my effort so dont vote it up, but v useful.
use Net::hostent; use Socket; print map (($h = gethost($_)) ? ("$_ -> " . join(', ', $h->name, @{$h- +>aliases}, map(inet_ntoa($_), @{$h->addr_list}) ). "\n") : $_ (unknown host)\n", @ARGV);