title: Regex with negative lookahead is not working
body: <pre><code>Edit the Expression &amp; Text to see matches.
  
  Expression sample
  </code></pre>
  
  <p>This is the text document which has two lines. I want to search for "Expression" word such that it does not follow "matches" word. So the output will be match to "Expression sample" line.
  Please help to generate regex for this. I have tried using following regex but this is not working. Many thanks</p>
  
  <pre><code>^(.*)Expression(.*)(?!matches)$
  </code></pre>