json.l fails to load on pil 64

[C K Kashyap]

Hi,
I get this error when I try to load json.l from
https://github.com/aw/picolisp-json/blob/master/json.l

[json.l:53] !? (de json-count-brackets (Str) (let Json_stack NIL (mapc
'((N) (if (or (= "{" N) (= "[" N)) (push 'Json_stack N) (case N ("]" (let R
(pop 'Json_stack) (unless (= "[" R) (err-throw "Unmatched JSON brackets
'['")))) ("}" (let R (pop 'Json_stack) (unless (= "{" R) (err-throw
"Unmatched JSON brackets '{'"))))))) Str) (when Json_stack (err-throw (text
"Unmatched JSON brackets '@1'" (pop Json_stack))))))

de -- Undefined

I think this must be a bug in picoLisp since it loads fine on the 32bit
picoLisp.

Regards,
Kashyap