What have you tried?

This is not a code-writing service; it's a tutorial, in the sense used by the British U.

Cf: On asking for help and How do I post a question effectively?

Update: I asked AnomalousMonk for a suggestion for better phrasing of what even I knew (at the time) to be fair game for requests to distinguish the "tutorial" in para 2 from the sense of "tutorial" at Wossamotta U. He offered an excellent response:

Maybe something like "... a tutorial, in the sense used by the British U, i.e., a collegiate effort at self-directed learning — and we, your colleagues, are here to help your effort."

Please direct any further upvotes to Re^2: How to add missing part in a Hash of Array and its author!