Using Graph::Easy version 0.76 1 -> 2 1 -> 3 1 -> 4 1 -> 7 2 -> 5 3 -> 5 4 -> 5 5 -> 6 6 -> 7 7 -> 8 8 -> 9 8 -> 10 9 -> 11 10 -> 11 +-----------------------------+ | | | | | +-------------------+-------------------+ | | v v +---+ +---+ +---+ +---+ +---+ +---+ +---+ +----+ +----+ | 4 | <-- | 1 | --> | 2 | --> | 5 | --> | 6 | --> | 7 | --> | 8 | --> | 10 | --> | 11 | +---+ +---+ +---+ +---+ +---+ +---+ +---+ +----+ +----+ | ^ | ^ | | | | v | v | +---+ | +---+ | | 3 | ----------------+ | 9 | -----------------+ +---+ +---+