> (let ([x 3] [y 4]) (+ x y))
7
> (let ([x 3]) x)
3
> x
. . x: undefined;
 cannot reference an identifier before its definition
> ((lambda (x) x) 3)
3
> ((lambda (x y) (+ x y)) 3 4)
7
> . b: unbound identifier in: b
> (hmm '(1 2 3))
. . hmm: undefined;
 cannot reference an identifier before its definition
> 
> (hmm2 '(1 2 3))
'(2 1)
>
> (hmm3 '(1 2 3))
'(2 1)
>
> (fact 5)
120
> ((lambda (x) x) 3)
3
> ((lambda x x) 3)
'(3)
> ((lambda l l) 3 4 5 6 )
'(3 4 5 6)
> ((lambda (x y . l) (list x y l)) 3 4 5 6 7)
'(3 4 (5 6 7))
>  ((lambda (x y . l) (list x y l)) 3 4)
'(3 4 ())