title: Custom + Method in Ruby String
body: <p>I am trying to modify the Ruby String class, specifically the + method.  I want it to return a specific string, such that</p>
  
  <pre><code> "a" + "b" =&gt; "custom_result"
  </code></pre>
  
  <p>Here's what I have:</p>
  
  <pre><code>class String
  
    def +(a)
      "custom_result"
    end
  
  end
  </code></pre>
  
  <p>When I try to require this file in irb, "custom_result" is in my prompt, and I can't execute anything.  Any ideas?</p>