title: What does the hexadecimal number in a reference to an array, hash, etc. indicate?
body: <p>When printing a reference to an array, hash, etc, what is that hexadecimal number in brackets?</p>
  
  <pre><code>perl -e 'print []'
  </code></pre>
  
  <p>Gives an output like: ARRAY(0x9acb830)</p>
  
  <p>What is 0x9acb830 exactly? If I print the same ref again, this number changes.</p>