title: Ruby yard: ENV['FOO'] without link
body: <p>I write a document with yard.</p>
  
  <p>I want to write environment variables as is.</p>
  
  <pre><code># ENV['FOO']
  </code></pre>
  
  <p>I expect this to ENV['FOO'] or <code>ENV['FOO']</code>. But this becomes a link like this with <code>yard server</code>.</p>
  
  <pre><code>[ENV](http://localhost:8808/docs/MyModule/'FOO')
  </code></pre>
  
  <p>How to avoid this?</p>