title: Match a pattern not followed by a sub-pattern in Vim
body: <p>Suppose I have a file with lines that contain the following strings:</p>
  
  <pre><code>...cat dog lorem ipsum...
  ...cat lizard ...
  ...cat bird ...
  ...cat dog ...
  </code></pre>
  
  <p>I want to write a regex that matches the lines in which <code>cat</code> is <em>not</em> followed by <code>dog</code>:</p>
  
  <pre><code>...cat lizard ...
  ...cat bird ...
  </code></pre>
  
  <p>How can I do this?</p>