title: How can I introspect a freemarker template to find out what variables it uses?
body: <p>I'm not at all sure that this is even a solvable problem, but supposing that I have a freemarker template, I'd like to be able to ask the template what variables it uses.</p>
  
  <p>For my purposes, we can assume that the freemarker template is very simple - just "root level" entries (the model for such a template could be a simple Map).  In other words, I don't need to handle templates that call for nested structures, etc.</p>