```common lisp
(describe simple-let
          (== (let ())
              nil)
          (== (let ()
                42)
              42))

(describe let-with-multiple-expr-body
          (== (let ()
                1
                2)
              2))

(describe let-bindings
          (== (let* ((x 1)
                     (y 2))
                (+ x y))
              3)
          (let ((x 2))
            (== (let ((x 1)
                      (y (+ x 1)))
                  y)
                3)))


(describe let-binding-scope
          (== (begin (let ((zz 2)) zz)
                     zz)
              nil))

(describe named-let
          (== (let loop
                ((numbers ’(3 -2 1 6 -5))
                 (nonneg ’())
                 (neg ’()))
                (cond ((null? numbers)
                       (list nonneg neg))
                      ((>= (car numbers) 0)
                       (loop (cdr numbers)
                          (cons (car numbers) nonneg)
                          neg))
                      (else
                       (loop (cdr numbers)
                          nonneg
                          (cons (car numbers) neg)))))
              '((6 1 3) (-5 -2))))
```

Fix typo (copy-paste single quotes).
user
```common lisp
(describe simple-let
          (== (let ())
              nil)
          (== (let ()
                42)
              42))

(describe let-with-multiple-expr-body
          (== (let ()
                1
                2)
              2))

(describe let-bindings
          (== (let* ((x 1)
                     (y 2))
                (+ x y))
              3)
          (let ((x 2))
            (== (let ((x 1)
                      (y (+ x 1)))
                  y)
                3)))


(describe let-binding-scope
          (== (begin (let ((zz 2)) zz)
                     zz)
              nil))

(describe named-let
          (== (let loop
                ((numbers '(3 -2 1 6 -5))
                 (nonneg '())
                 (neg '()))
                (cond ((null? numbers)
                       (list nonneg neg))
                      ((>= (car numbers) 0)
                       (loop (cdr numbers)
                          (cons (car numbers) nonneg)
                          neg))
                      (else
                       (loop (cdr numbers)
                          nonneg
                          (cons (car numbers) neg)))))
              '((6 1 3) (-5 -2))))
```
assistant