class PriorityQueue {
    has tasks = []

    method insert (Number priority { _ >= 0 }, task) {
        for n in range(tasks.len, priority) {
            tasks[n] = []
        }
        tasks[priority].append(task)
    }

    method get      { tasks.first { !.is_empty } -> shift }
    method is_empty { tasks.all   {  .is_empty } }
}

var pq = PriorityQueue()

[
    [3, 'Clear drains'],
    [4, 'Feed cat'],
    [5, 'Make tea'],
    [9, 'Sleep'],
    [3, 'Check email'],
    [1, 'Solve RC tasks'],
    [9, 'Exercise'],
    [2, 'Do taxes'],
].each { |pair|
    pq.insert(pair...)
}

say pq.get while !pq.is_empty