title: Regex to Match White Space or End of String
body: <p>I'm trying to find every instance of @username in comment text and replace it with a link. Here's my PHP so far:</p>
  
  <pre><code>$comment = preg_replace('/@(.+?)\s/', '&lt;a href="/users/${1}/"&gt;@${1}&lt;/a&gt; ', $comment);
  </code></pre>
  
  <p>The only problem is the regex is dependent upon there being whitespace after the @username reference. Can anyone help me tweak this so it will also match if it is at the end of the string?</p>