title: regex line start in character set
body: <p>Let's say I want to search for a 'b' that occurs either at start of line or followed by 'a'.</p>
  
  <p>Why doesn't <code>re.match('[\^a]b','b')</code> match while <code>re.match('^b','b')</code> does?</p>
  
  <p><strong>Update:</strong> I realised I should have been using <code>search</code> instead of <code>match</code>. I want it to be a positive for things like 'b', 'cab', 'ab', 'bc', and 'abd'.</p>