Your problem is in the first map (or the last map reading left to right which is not how I think when I'm building a Schwartzian transform). The /.+,/ in

map     { [ $_, /.+,/ ] }
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is only returning the number of matches (or 1 in this case). As a result it should give you back the original list. If you're trying to sort on computed fields, you need to extract them first and _then_ bundle them up in the anonymous array.

So something like
map     { my @fields = split /,/; [ $_, $field[1] ] } might get you closer to what you're looking for.

Once you've mastered that, you'll next want to look at the Orcish manoeuvre which speeds up your sorts