title: Django TemplateTag evaluating to a boolean
body: <p>Is it possible to create a Django template tag which evaluates to a boolean?</p>
  
  <p>Eg, can I do:</p>
  
  <pre><code>{% if my_custom_tag %}
      ..
  {% else %}
      ..
  {% endif %}
  </code></pre>
  
  <p>At the moment I've written it as an as tag, which works fine like this:</p>
  
  <pre><code>{% my_custom_tag as var_storing_result %}
  </code></pre>
  
  <p>But I was just curious if I could do it the other way as I think it'd be nicer if I didn't have to assign the result to a variable first.</p>
  
  <p>Thanks!</p>