title: Regex that validate a string consist of 3-4 char followed by semicolon
body: <p>I would like to make a regex that validate a string is in this format:</p>
  
  <pre><code>".xml;.mp4;.webm;.wmv;.ogg"
  </code></pre>
  
  <p>file format separated with semicolon.</p>
  
  <p>what is the best way to do this?</p>