title: Need to add underscore to my regex
body: <p>I'm new to regular expression and just can't seem to figure this out:</p>
  
  <pre><code>'/^[A-Za-z0-9](?:.[A-Za-z0-9]+)$/'
  </code></pre>
  
  <p>As it's right now it allows dots anytime after the first char and I like to add <code>_</code> so that it allows both.
  Thanks</p>