{-# LANGUAGE RankNTypes #-}
data Person = Person { _name :: String , _age :: Int } deriving Show

makeLenses 'Person

example :: Person
example = Person "Bob" 55

pry :: Lens' r x -> Iso' r (x -> r,x)
pry l = iso (\r -> (\x -> set l x r, view l r)) (uncurry ($))

consName :: Prism' Person (Char,Person)
consName =
     pry name . aside _Cons . iso (\(a,(b,c)) -> (b,(a,c))) (\(b,(a,c)) -> (a,(b,c))) . seconding (Control.Lens.from (pry name))

-- Λ review consName ('z',example)
-- Person {_name = "zBob", _age = 55}
--
-- Λ preview consName example
-- Just ('B',Person {_name = "ob", _age = 55})