I'd use LWP::UserAgent to make the request(s). You'll get a HTTP::Response object; call ->headers() on that and you'll end up with a HTTP::Headers object that you can query as needed.

Here's some skeleton code to get you started (<s>*completely* untested!</s> now marginally tested):

#!/usr/bin/perl

use feature qw/say/;
use strict;
use warnings;
use LWP::UserAgent;

my $ua = LWP::UserAgent->new;
$ua->timeout(10);
$ua->env_proxy();

open my $ips, "<", "ips.txt" or die "Cannot open ips.txt: $!";

while(<$ips>) {

  chomp;

  my $response = $ua->get("http://$_/");
  unless($response->is_success) {
    warn "Failed to process $_: " . $response->status_line;
    next;
  }

  say "Headers for $_:";

  my $headers = $response->headers();
  foreach my $header ($headers->header_field_names()) {
    say "\t$header: " . $headers->header($header);
  }

  say "";
}
[download]

Processing the results in the desired fashion is left as an exercise for the reader.