title: How do I write a regular expression for a URL without the scheme?
body: <p>How can I write a RE which validates the URLs without the scheme:</p>
  
  <p>Pass:</p>
  
  <ul>
  <li>www.example.com</li>
  <li>example.com</li>
  </ul>
  
  <p>Fail:</p>
  
  <ul>
  <li><a href="http://www.example.com" rel="nofollow noreferrer">http://www.example.com</a></li>
  </ul>