type M<'a>  =
    | Error
    | ValidResult of 'a

let (?>) m f =
    match m with
    | ValidResult (v) -> ValidResult (f v)
    | Error -> Error

// Example:
let add a b = a + b

ValidResult 1
    ?> add 2
    ?> printfn "success %i"

Error
    ?> add 2
    ?> printfn "this line will never be executed %i"