title: regular expression for 4 number, a comma and 4 numbers
body: <p>Using a regular expression, I would like to match the following string:   </p>
  
  <pre><code>4232,2232
  </code></pre>
  
  <p>I have tried </p>
  
  <pre><code>^[0-9]+(,[0-9]+)$
  </code></pre>
  
  <p>However, it doesn't work as expected. I want to cater for 4 numbers, a comma and 4 numbers.</p>