title: Regex excluding specific characters
body: <p>In <a href="http://regexone.com/lesson/4?" rel="noreferrer">this lesson</a> I don't understand why <code>[^b]</code> is not correct? I understand that <code>[^bog]</code> is correct.</p>
  
  <p><code>[^b]</code> should match any string that has no <code>b</code> character and don't match any string containing any <code>b</code> character.</p>
  
  <p>Is there anything wrong in my understanding?</p>