Created Saturday 27 December 2014
Look ahead & look behind
- Positive lookahead - match 'q' that is followed by 'u'
- Negative lookahead - match 'q' that isn't followed by 'u'
- Positive lookbehind - match 'b' in 'cab', but doesn't match 'bed' or 'debt'
- Negative lookbehind - match 'b' that isn't preceded byh 'a'