Late to the party, but what about simply thinking of (map) as indexing into the
cartesian product ({'abc';'ABCD')?
(({'abc';'ABCD') {~ $ <@#: I.@,) map
┌──┬──┬──┬──┐
│aA│aD│bB│bC│
└──┴──┴──┴──┘
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