title: Is there a regex to match a string that contains A but does not contain B
body: <p>My problem is that i want to check the browserstring with pure regex.</p>
  
  <pre><code>Mozilla/5.0 (Linux; U; Android 3.0; en-us; Xoom Build/HRI39) AppleWebKit/534.13 (KHTML, like Gecko) Version/4.0 Safari/534.13
  </code></pre>
  
  <p>-> should match</p>
  
  <pre><code>Mozilla/5.0 (Linux; U; Android 2.2.1; en-us; Nexus One Build/FRG83) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1 
  </code></pre>
  
  <p>should not match</p>
  
  <p>my tried solution is: <code>/?((?&lt;=Android)(?:[^])*?(?=Mobile))/i</code>
  but it matches exactly wrong.</p>