Another one-liner to define a very simple hygienic threading macro:
(define-syntax-parse-rule (with it:id body:expr ...)
(let* ([it body] ...) it))
Usage example:
(with it "Hello World"
(string-downcase it)
(string-split it)
(map string->list it)
(displayln it))
; displays: ((h e l l o) (w o r l d))