Expression<Action> expLoop = () =>
    Block.Start(new { i = 0 }, b =>
        Block.Default
            .Loop(() =>
                Block.Default
                    ._(() => Console.WriteLine("loop: " + b.i))
                    .Assign(() => b.i, b.i + 1)
                    .IfThen(b.i >= 4, () => Block.Default.Goto("break"))
                )
            .Label("break")
            ._(() => Console.WriteLine("end"))
    );