title: format strings and math in here document
body: <p>This is really two questions combined. </p>
  
  <p>First is: Is there any way to do math inside of a here document? </p>
  
  <p>Second: Is there any way to use format strings in a here document? 
  An example of this second question is this:</p>
  
  <pre><code>print &lt;&lt;HERE
  %s
  HERE
  % 'string'
  </code></pre>
  
  <p>yet that doesn't work. </p>
  
  <p>Thankss</p>