let-hash

(defsyntax (let-hash stx)
  (syntax-case stx ()
    ((macro expr body ...)
     (with-syntax ((@ref (stx-identifier #'macro '%%ref)))
       #'(let (hash expr)
           (let-syntax
               ((var-ref
                 (syntax-rules ()
                   ((_ id) (@ref id)))))
             (let-syntax
                 ((@ref
                   (lambda (stx)
                     (syntax-case stx ()
                       ((_ id)
                        (let (str (symbol->string (stx-e #'id)))
                          (if (eq? (string-ref str 0) #\.)
                            (with-syntax ((sym (string->symbol (substring str 1 (string-length str)))))
                              (if (eq? (string-ref str 1) #\.)
                                ;; quoted (multiple dots)
                                #'(var-ref sym)
                                #'(hash-ref hash 'sym)))
                            #'(var-ref id))))))))
               body ...)))))))

(def my-hash (hash (a 1) (b 2) (c (hash (a 11) (b 12) (c 13)))))
(let-hash my-hash [.a .b (let-hash .c [.a .b .c ..a ..b])])
=> '(1 2 (11 12 13 1 2))

It's in :std/sugar as of mighty-gerbils/gerbil@f99f38d.
Example usage: https://github.com/vyzo/gerbil/blob/master/src/tools/gxpkg.ss#L85