title: Getting placeholder list from a Velocity template
body: <p>suppose I have a Velocity template like this:</p>
  
  <pre class="lang-none prettyprint-override"><code>Hi!, my name is ${name} and I'm ${age} years old.
  </code></pre>
  
  <p>Note the template has no loops or conditional statements.</p>
  
  <p>I would like to get a list with these values</p>
  
  <pre class="lang-none prettyprint-override"><code>["name", "age"]
  </code></pre>
  
  <p>I checked the API but looks like the Template class does not have a method for this: <a href="https://velocity.apache.org/engine/releases/velocity-1.7/apidocs/org/apache/velocity/Template.html" rel="nofollow">https://velocity.apache.org/engine/releases/velocity-1.7/apidocs/org/apache/velocity/Template.html</a></p>
  
  <p>How can I get this list with using velocity without parsing the template myself?</p>