title: Match partial string with regex
body: <p>I've a little problem with a simple regex. </p>
  
  <p>I'd like a regex to match this simple string (in a xml file)  where wsse: could be optional and in particular something like this: &lt; wsse:Username > (wsse is optional).</p>
  
  <p>Could you help me?</p>
  
  <p>Thanks in advance for your kind help!</p>