title: Regular expression to match credit card expiration date
body: <p>I have the following pattern which I'm trying to use to match credit card expiration dates:</p>
  
  <pre><code>(0[1-9]|1[0-2])\/?(([0-9]{4})|[0-9]{2}$)
  </code></pre>
  
  <p>and I'm testing on the following strings:</p>
  
  <pre><code>02/13
  0213
  022013
  02/2013
  02/203
  02/2
  02/20322
  </code></pre>
  
  <p>It should only match the first four strings, and the last 3 should not be a match as they are invalid. However the current pattern is also matching the last string. What am I doing wrong?</p>