title: When did "assigned but unused" become a warning for Ruby?
body: <p>In what version or patchlevel did the following warning get added?</p>
  
  <pre><code>warning: assigned but unused variable - x
  </code></pre>
  
  <p>I heard about it from <a href="http://www.slideshare.net/tenderlove/nordic-ruby-2011" rel="nofollow">http://www.slideshare.net/tenderlove/nordic-ruby-2011</a></p>