public static void InsertItem<T>(ref Item<T> start, T val, Func<T, Item<T>, bool> insertBefore)
    {
        Console.WriteLine($"Creating item: {val}");
        Item<T> current = start, previous = null;

        while (current != null && !insertBefore(val, current))
        {
            previous = current;
            current = current.next;
        }
        Item<T> item = new Item<T>(val, current);

        if (previous == null)
        {
            start = item;
        }
        else
        {
            previous.next = item;
        }
    }