[Haskell-beginners] flatten comma operator

In 'Real World Haskell' I found code like LiftA2 (,) .... Looks odd. But after some experimenting in winghci I found that (,) 1 2 is valid code and is equal to (1,2). Now I wonder how to create (1,2,3). I think you need a join or a flatten function or ...? Join doesn't work? Kees