MIT Proto lacks a basic getting started guide. How do I find a shell that accepts commands like (def foo...) and proto -n 1000 -l -m ...?

http://groups.csail.mit.edu/stpg/proto.html

I can run in my bash shell:

./proto -n 1000 -s 0.1 -T -l "(red (gradient (= (mid) 0)))"

I can't figure out how to run e.g. channel.proto:

(def channel (src dst width)
  (let* ((d     (distance src dst))
         (trail (<= (+ (gradient src) (gradient dst)) (+ d 0.01))) ;; float error
         ;; (trail (= (+ (gradient src) (gradient dst)) d))
         )
    (dilate trail width)))

;; To see a channel calculated from geometric primitives, run:
;; proto -n 1000 -l -m -s 0.5 "(blue (channel (sense 1) (sense 2) 10))"
;; click on a device and hit 't' to set up the source, then click on
;; another device and hit 'y' to designate the destination. At first
;; every device will be blue, but then it should clear and you should
;; see a thick blue path connecting the two devices you selected.

Thanks!

P.S. Somebody please tag this mit-proto. I can't.