#!/usr/bin/perl
use Socket;

sub addr_is_private ( $ ) {
    my $addr = shift;
    ($addr & "\xff\0\0\0") eq pack "CCCC", 10, 0, 0, 0
      or ($addr & "\xff\xf0\0\0") eq pack "CCCC", 172, 16, 0, 0
	or ($addr & "\xff\xff\0\0") eq pack "CCCC", 192, 168, 0, 0;
}

sub host_exists_and_is_not_private ( $ ) {
    my $host = shift;
    my $addr = inet_aton($host);
    defined $addr and not addr_is_private($addr);
}

while (<>) {
    my @hosts = ();
    my $nonpriv = 0;
    while (s/^([^,\s]+),?//) {
	my $host = $1;
	push @hosts, $host
	  if $host =~ /^[-\w]+$/
	    or host_exists_and_is_not_private($host) and $nonpriv++, 1;
    }
    print join(",", @hosts) . $_ if $nonpriv > 0;
}