title: Cannot understand some variables
body: <p>I have a code line:</p>
  
  <pre><code>$data-&gt;{nav}-&gt;{'current'}-&gt;{performance_gross}
  </code></pre>
  
  <p>I understand <code>$data</code> is scalar and <code>nav</code>, <code>performance_gross</code> are hash keys. But what is <code>'current'</code>?</p>