To give you some hints (if you haven't been quick enough to read the first version of this node :)

• match literal parenthesis - you have to escape them because of their special meaning
• then match anything in between with non-greedy quantifiers
• match corresponding parenthesis
• you hopefully don't have nested parens because then it gets tricky

Update: OK, so now I probably spoiled the learning already as davorg and jeroens remarked. I generally agree with it so I put the code now in the 'spoiler' section and altered the explanation into a hint list - but probably too late anyway ;-).

-- Hofmator