title: Regex to add padding zeroes
body: <p>I am working on this yahoo pipe Regex and I found a bug I'm unable to wrap my mind around it.</p>
  
  <p>I have a URL, from which I extract digits, cat them and make a img html tag and embed it. The issue is that, the URL is presented in a non padded way, but the image linked has the zeroes. Therefore, when there is a day or a month with single digits, the regex stops working.</p>
  
  <p>This is what I have so far:</p>
  
  <pre><code>The URL: http://www.penny-arcade.com/comic/2009/1/2/patently-ridiculous/
  The RegEx: (\d{4})/(\d+)/(\d+)
  The Replacement: &lt;img src="http://www.penny-arcade.com/images/$1/$1$2$3.jpg" /&gt;
  
  What should appear: &lt;img src="http://www.penny-arcade.com/images/2009/20090102.jpg" /&gt;
  What appears: &lt;img src="http://www.penny-arcade.com/images/2009/200912.jpg"/&gt;
  </code></pre>
  
  <p>How could I parse those zeroes as to make this thing work?</p>