title: Check if string is hex that starts with "0x..." Perl
body: <p>How would I check if a string:</p>
  
  <ol>
  <li>Starts with "0x"</li>
  <li>Is a valid hex number </li>
  </ol>
  
  <p>So for example:</p>
  
  <pre><code># Returns false
  $string = "0213"
  
  # Returns false
  $string = "0xHHH"
  
  # Returns true
  $string = "0x123456789abcdefABCDEF"
  </code></pre>