arc> (sort < '("orange" "pea" "apricot" "apple")) Error: "set-car!: expected argument of type <pair>; given: 577273856"
arc> (let x '("orange" "pea" "apricot" "apple") (= (car x) 1)) 1 arc> (let x '("orange" "pea" "apricot" "apple") (= (car x) 1) x) Error: "invalid memory reference. Some debugging context lost"
Edit 14 minutes later: looks like 7.7 shows identical errors.
Edit 45 minutes later: all this works fine with Racket 6.0. That version was already dealing with immutable lists by default (https://download.racket-lang.org/releases/6.0/doc/compatibil...), so I'm inclined to consider this a regression in Racket.