title: Unexpected alert with message "undefined" after successfully calling simple function with arguments
body: <p>Can anyone tell me why the following code produces the alert box that I expect (RyeTofuRye), but then produces a second alert box with the message "undefined?"  At least that's what it's doing in the latest FireFox on my Windows 7 machine.</p>
  
  <pre><code>function makeSandwich(bread, meat) {
  alert(bread + meat + bread);
  }
  var mySandwich = makeSandwich('Rye', 'Tofu');
  alert(mySandwich);
  </code></pre>