queues
(let* ((queue (car queues))
(remaining-queues (cdr queues))
(ptrs (queue-ptrs queue))
(new-ptrs (execute-instr core (car ptrs) (queue-owner queue))))
(if (null? new-ptrs)
queues
(let* ((queue (car queues))
(remaining-queues (cdr queues))
(ptrs (queue-ptrs queue))
(new-ptrs (execute-instr core (car ptrs) (queue-owner queue))))
(if (null? new-ptrs)