title: Regex for userid validation
body: <p>I know I should study up on regex but quite frankly, I only need to write one every third blue moon.  Today is that 3rd blue moon. </p>
  
  <p>Looking for a regex that will validate the following userid in javascript:</p>
  
  <pre><code>AA1234 or     
  aa1234 or    
  aa123a or    
  aa123A or    
  any other combination of capital or lower case letters.
  </code></pre>
  
  <p>If I were to put this in words, it would be spelled out like 2 letters, 3 digits, followed by a letter or a digit.</p>
  
  <p>Can someone help me with this today?</p>
  
  <p>Per comment below, updated request for JavaScript</p>