#!/usr/bin/perl

use strict;
use warnings;
use CGI::Fast;

while ( my $q = CGI::Fast->new ) {
    my $client_ip = $q->http('X-Forwarded-For') || $q->remote_addr || 'unknown';

    print $q->header("text/plain; charset=utf-8");
    print "$client_ip\n";
}