title: Regex: what does (?! ...) mean?
body: <p>The following regex finds text between substrings FTW and ODP.</p>
  
  <pre><code>/FTW(((?!FTW|ODP).)+)ODP+/
  </code></pre>
  
  <p>What does the <code>(?!</code>...<code>)</code> do?</p>