title: What's causing this Scala error message?
body: <p>I seem to have found my way to a weird error message. I'm storing a password, and I have a comment that says</p>
  
  <pre><code>/** A password hash is stored as `"algorithm$iterations$salt$hash"`
   *  with the number of iterations optional for some algorithms
  </code></pre>
  
  <p>When I tried to create a distribution jar for my project, I got this warning:</p>
  
  <pre><code>Variable iterations undefined in comment for...
  </code></pre>
  
  <p>I tracked the warning down to the trait <code>package scala.tools.nsc.ast.DocComments</code>, where I discovered it is apparently possible to put variables of some sort in ScalaDoc. Unfortunately, Googling for "variables in Scaladoc" or "ScalaDoc dollar sign" returns nothing useful.</p>
  
  <p>Does anyone know what feature I'm using incorrectly and how I can include a dollar sign
  in a ScalaDoc comment without getting a warning?</p>