perhaps i'm dense, but i don't see how this gives you any more multidimensional functionality than hashes of hashes, e.g.:

$hash{6}{times}{9} = 42;
$hash{2}{plus}{2} = 5;
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the one thing i often find i want to do with the hash-of-hash notation that i can't, easily, is make slices that keep their shape via place-holders, like:

$hash{0}{plus}{0} = 0;
$hash{0}{plus}{1} = 1;
$hash{1}{plus}{0} = 1;
$hash{1}{plus}{1} = 10;

%plus = %hash{}{plus}{};
#  (or something like it)
# should yield: 
# $plus{0}{0} = 0;
# $plus{0}{1} = 1;
# $plus{1}{0} = 1;
# $plus{1}{1} = 10;
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or something like that. hash-wise hash slices. but i don't see your trick helping, there.