[racket] Help needed representing data | 2d hashes?

I don't speak Perl and didn't make it through the whole post. Is the
core problem, when you strip away the app. specific stuff, that you
want a hash of hashes? That's straightforward to implement:

(define top (make-hash))

(hash-set! top 'foo (make-hash))

and so on...

Alternatively you can make your keys tuples:

(hash-set! top '(foo bar) 'a-value)

N.