title: How to wrap text in a hyperlink ONLY if it isn't already wrapped in a hyperlink
body: <p>I need to do a regex replacement where I take a string and wrap a hyperlink around it (but here's the catch) as long as it isn't already surrounded by a hyperlink. How would I do this?</p>
  
  <p>So, for example, let's take the text:</p>
  
  <pre>
  The quick brown fox.
  </pre>
  
  <p>I want to make "quick brown" a link, like this:</p>
  
  <pre>
  The &lt;a href="http://www.stackoverflow.com/"&gt;quick brown&lt;/a&gt; fox.
  </pre>
  
  <p>But if I find the text:</p>
  
  <pre>
  The &lt;a href="http://www.stackoverflow.com/"&gt;quick brown&lt;/a&gt; fox.
  </pre>
  
  <p>I want to be sure that I don't wrap "quick brown" in another hyperlink.</p>
  
  <p>How would I do this?</p>