example.pl

use Mojolicious::Lite -signatures, -async;

# Render template "index.html.ep" from the DATA section
get '/' => sub ($c) {
  $c->render(template => 'index');
};

# WebSocket service used by the template to extract the title from a web site
websocket '/title' => sub ($c) {
  $c->on(message => async sub ($c, $msg) {
    my $tx    = await $c->ua->get_p($msg);
    my $title = $tx->result->dom->at('title')->text;
    $c->send($title);
  });
};

app->start;
__DATA__
@@ index.html.ep
% my $url = url_for 'title';
<script>
  var ws = new WebSocket('<%= $url->to_abs %>');
  ws.onmessage = function (event) { document.body.innerHTML += event.data };
  ws.onopen    = function (event) { ws.send('https://mojolicious.org') };
</script>