Haskell does not constrain the order of evaluation when dealing with real world. It constrains order of effects. The code "putStrLn this >> putStrLn that" is a

Haskell does not constrain the order of evaluation when dealing with real world. It constrains order of effects. The code "putStrLn this >> putStrLn that" is allowed to evaluate this and that in any order, basically. "that" may depend on "this" and vice versa. The very expressions "putStrLn a" is also not an action, but expression, being evaluated into actions. And the constrainment of effects is what makes Haskell special.