title: How do I tell if Ruby 2.0 is copy on write friendly?
body: <p>I'm doing this in my <code>irb</code> after installing Ruby 2.0:</p>
  
  <pre><code>% irb                                                                                              
  2.0.0p247 :001 &gt; GC.respond_to?(:copy_on_write_friendly=)
   =&gt; false
  </code></pre>
  
  <p>Why is this returning false? How do I know then that Ruby 2.0 is CoW friendly?</p>