title: LESS CSS guards without mixin
body: <p>I'm just getting into LESS and am trying to figure out how I can make conditional css statements without mixins. I find that I have a lot of single line css statements that only occur once but are dependent on some variable or condition and that using mixins is a bit pointless since it will never be reused.</p>
  
  <p>Example.</p>
  
  <pre><code>@add-margin: true;
  
  body {
      margin-top: 20px;  //I only want this if add-margin is true
  }
  </code></pre>
  
  <p>So ideally I want this:</p>
  
  <pre><code>body when (@add-margin) {
       margin-top: 20px;
  }
  </code></pre>
  
  <p>But that doesn't work. Using a mixin works but seems silly to make one just for a one liner.  Is there some alternative way I can do this?</p>
  
  <p>Thanks</p>