title: Swap/match "left" with "right" within a bracket block with regex
body: <p>I'm trying to swap "left" with "right" and "right" with "left" so:</p>
  
  <pre><code>.left {
    left: 10px;
    float: right;
  }
  </code></pre>
  
  <p>would be come:</p>
  
  <pre><code>.left {
    right: 10px;
    float: left;
  }
  </code></pre>
  
  <p>What kind of expression would match "left" or "right" but not ".left" only within brackets?</p>