title: Is the string '@LIBDIR@' somehow magic?
body: <p>For some reason I looked at <a href="http://selenic.com/hg/file/1d7a36ff2615/hg" rel="nofollow"><code>/usr/bin/hg</code></a> and saw what seemed like a strange bit of code:</p>
  
  <pre><code>libdir = '@LIBDIR@'
  
  if libdir != '@' 'LIBDIR' '@':
      ...
  </code></pre>
  
  <p>The if statement looks like a tautology/contradiction as <code>'@LIBDIR@'</code> should always equal <code>'@' 'LIBDIR' '@'</code> in Python, so the code will never run.  Under what conditions does <code>'@LIBDIR@'</code> change into something else?</p>