let defer f = { new System.IDisposable with member __.Dispose() = f () }

let checkAnswer answerToEverything =
    use cleanup = defer (fun () ->
        // TODO: insert clean-up code here
        printfn "Did clean-up, leaving scope...")
    
    if answerToEverything = 42 then
        printfn "Well done!"
    else
        printfn "Oh, no!" 
        failwith "Catastrophic culture failure."

checkAnswer 42
checkAnswer 365