wow, your reply is quite impressive. there is much to learn from. i especially like :

  $array->[ ... ] ||= [];
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to either create a array or grab the existing one before the recursive call.

and i have a deeper appreciation for the use of {} and [] to group elements together :

  $array->[$hash-> { $keys->[$dim] } ]

  $array->[ $keys->[$dim] ]
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thank you very much! i glad i took the time to re-state my question.

BTW, before my repost, i read "I know what I mean. Why don't you?" and now to have the author of that article respond to this question is astonishing.