How do I write a parser that doesn't fail?

[madchicken]

Can someone point me in the direction of writing a parser where I can collect all good pairs and not fail even if the input is not valid for the grammar? I would like to have an output like pair1, pair2, pair3, error. I was taking a look to the ParserState, but I cannot really understand how to use it in my case, where I have a pretty complex grammar. Thanks in advice.