Slope

(define let
  (macro (args ...)
    (define in (map (lambda (inargs) (car inargs)) args))
    (define out (map (lambda (outargs) (eval (car (cdr outargs)))) args))
    (define l (eval ['lambda in (cons 'begin ...)]) )
    (apply l out)))

(define while
  (macro (test ...)
    (define el
      (eval ['lambda [] ['if test (list-join ['begin] ... [['el]])]]))
    (el)))

(define when
  (macro (test ...)
    (eval ['if test (cons 'begin ...)])))

(define unless
  (macro (test ...)
    (eval ['if ['not test] (cons 'begin ...)])))


(define do-count (lambda (count lam)
  (for-each lam (range count))))

(define x -5)
(while (< x 5) (display-lines x) (set! x (+ x 1)))

(when (> x 0) (display "X is " x " (which is greater than 0)\n") (display "Yay!\n"))
(unless (< x 0) (display "X is " x "(which is greater than 0)\n") (display "Yay!\n"))

(do-count 5 (lambda (x) (display-lines (+ x 1))))

(display-lines (let ((a 12)(b 3)) (+ a b)))