title: regex replace urls with anchors ONLY if not already in anchors
body: <p>I've seen similar questions asked before, but none with a working solution.</p>
  
  <p>I am trying to replace all urls on a page with anchor tags, but only those which aren't already within anchor tags.</p>
  
  <p>so <a href="http://google.com" rel="nofollow">http://google.com</a> should be replaced with</p>
  
  <pre><code>&lt;a href="http://google.com"&gt;http://google.com&lt;/a&gt;
  </code></pre>
  
  <p>But only if it's not already within an anchor tag.</p>
  
  <p>Any thoughts?</p>