Crossposted to stackoverflow and got a reply that satisfied me.

The author, LeoNerd, suggests using either Future or Async::MergePoint which both fullfill my needs - Future in a more generalized way, and MergePoint exactly in the form I imagined when writing my post.

In reply to Re: Callback multiplexer by Dallaylaen
in thread Callback multiplexer by Dallaylaen

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