title: Can't post json in a Mojo::UserAgent request
body: <p>I can't get the following <code>Mojo::UserAgent</code> call to post JSON to the server:</p>
  
  <pre><code>use Mojo::UserAgent;
  my $ua=Mojo::UserAgent-&gt;new;
  my $json = $ua-&gt;post("localhost:6767" =&gt; {} =&gt; json =&gt;{ val=&gt;10 })-&gt;res-&gt;json;
  </code></pre>
  
  <p>Using a fake debug server on the other side with <code>nc -l 6767</code> gives the following output:</p>
  
  <pre><code>POST / HTTP/1.1
  User-Agent: Mojolicious (Perl)
  Connection: keep-alive
  Content-Length: 0
  Host: localhost:6767 
  </code></pre>
  
  <p>It's not just the <code>json</code> method, the <code>form</code>, and the whole Transactor seems to be broken on 2 of my machines. From the docs:</p>
  
  <pre><code>perl -MMojo::UserAgent::Transactor -E 'say Mojo::UserAgent::Transactor-&gt;new-&gt;tx(PUT =&gt; "http://kraih.com" =&gt; json =&gt; {a =&gt; "b"})-&gt;req-&gt;to_string;'
  PUT / HTTP/1.1
  Content-Length: 4
  Host: kraih.com
  
  json
  </code></pre>
  
  <p>Hard to believe my eyes. What am I missing?</p>