And because reasons… and because <readmore/> is so hard to spell…

File 1066091.cgi

#!/usr/bin/env perl
use strictures;
use CGI qw(:standard);
use Data::Validate::IP "is_ipv4", "is_ipv6";
use Data::Validate::Domain "is_domain";
use JSON;

if ( my $thing = param("ip_or_domain") )
{
    print header("application/json"),
        to_json({ ipv4 => is_ipv4($thing) ? \1 : \0,
                  ipv6 => is_ipv6($thing) ? \1 : \0,
                  domain => is_domain($thing) ? \1 : \0 });
}
else
{
    print header("text/html"),
        start_html(-title => "OHAI",
                   -script => { -type => "text/javascript",
                                -src => "//ajax.googleapis.com/ajax/li
+bs/jquery/1.10.2/jquery.min.js" }),
        h1("MUCH IP. SO OCTET. WOW."),
        start_form(),
        p({-style => "width:48%; display:inline-block; text-align:righ
+t",
             -class => "label"},
            "IP or Domain"),
        p({-style => "padding-left:1%;width:50%; display:inline-block"
+},
            textfield(-name => "ip_or_domain",
                      -style => "width:17em",
                      -placeholder => "Enter an IP or Domain to verify
+")),
        p({-style => "text-align:center", -class => "results"}),
        end_form(),
        <<'    __jQuery', # The leading four spaces have to match at e
+nd.
        <script type="text/javascript">jQuery(function($){
          var $in = $("input[name=ip_or_domain]");
          var $form = $in.closest("form");
          $form.submit(function(e){ e.preventDefault() });
          $in.keyup(function(e){
              $(".results").children().remove();
              $.ajax({
                  dataType: "json"
                 ,url: "/"
                 ,data: { ip_or_domain:$in.val() }
                 ,success: function(data){
                     for ( var key in data )
                     {
                         if ( data.hasOwnProperty(key) && data[key] )
                         {
                             var $i = $("<div style='color:#900'></div
+>");
                             $i.hide();
                             $(".results").append($i);
                             $i.text("Looks like " + key).fadeIn();
                         }
                     }
                     if ( ! $(".results").children().length )
                         $(".results").hide().append("<i>nothing</i>")
+.fadeIn();
                 }
              });

          });
        })</script>
    __jQuery
    end_html()
    ;
}

exit 0;
[download]

Update: moved the end_html().

Run it and visit it, probably at http://localhost:8080…

plackup -l :8080 -L Shotgun -MPlack::App::WrapCGI \
  -e 'Plack::App::WrapCGI->new( script => "1066091.cgi" )'
[download]

Don’t write code like this so close to Christmas. You will make the baby Jesus cry.