title: variable in class name jade
body: <p>I can't set a variable name in a class in jade:</p>
  
  <pre><code>.flag_#{ session.locale } #{ session.locale }
  </code></pre>
  
  <p>I have:</p>
  
  <pre><code>&lt;div class="flag_" &gt;en&lt;/div&gt;
  </code></pre>
  
  <p>And I'd like to have</p>
  
  <pre><code>&lt;div class="flag_en" &gt;en&lt;/div&gt;
  </code></pre>
  
  <p>Thanks</p>