(letseq [a 0
       b a]
  (assert (== b 0)))

(let [a 5]
  (let []
    (def a 6)
    (assert (== a 6)))
  (assert (== a 5)))

(newScope
  (def b 12)
  (newScope
    (def b 99)
    (newScope
      (def b 7)
      (assert (== b 7)))
    (assert (== b 99)))
  (assert (== b 12)))