ZeroMQ Choosing Correct Client-Worker Model for a Call Center

I have a project that needs to be written in Perl so I've chosen ZeroMQ.

There is a single client program, generating work for a variable number of workers. The workers are real human operators who will complete a task then request a new task. The job of the client program is keep all available workers busy all day. It's a call center.

So each worker can only process one task at time, and there may be some time before requesting a new task. And the number of workers may vary during the day.

The client needs to keep a queue of tasks ready to give to workers as and when they request them. Whenever the client queue gets low the client can generate more tasks to top-up the queue.

What design pattern (i.e. what ZeroMQ Socket combination) should I use for this? I've skimmed through all the patterns in the 0MQ Guide and can't find anything that matches this.

Thanks