The future parser will allow literal regular expressions almost
everywhere. The lexer was constrained to only recognize such
expressions when preceeded by one of the tokens:

',', 'node', '{', '}', '=~', '!~', or 'inherits'

This commit will add the following tokens to that list

'(', '[', '=>', '?', '=',  '==', and '!='.

and relevant unit tests.