This program does not print the same output when `--enable-self-tail` is used. ``` #lang racket/base (define xs (list (list 1 2 3 4 5) (list 5 4 3 2 1))) (let loop ([xs xs] [f void]) (cond [(null? xs) (f)] [else (define x (car xs)) (loop (cdr xs) (λ () (displayln x) (f)))])) ``` When the flag **is not** used (or when running the code in Racket) the output is: ``` (5 4 3 2 1) (1 2 3 4 5) ``` When the flag **is** used the output is: ``` (5 4 3 2 1) (5 4 3 2 1) ```