Add "return" to Racket when you need a guard-clause

return-macro.rkt

#lang racket
(require racket/stxparam)

(provide return
         define/guard)

(define-syntax-parameter return
    (λ (stx)
      (raise-syntax-error (syntax-e stx) "can only used inside \"define/guard\"")))

(define-syntax-rule (define/guard (name args ...) body0 body ...)
    (define (name args ...)
      (let/cc ret
        (syntax-parameterize ([return (make-rename-transformer #'ret)])
          body0
          body ...))))

(define/guard (test2 a b)
  (when (> a b) (return 456))
  (displayln "hehehe")
  123)

(define (test a b)
  (let/cc return
    (when (> a b) (return 456))
    (displayln "hehehe")
    123))