(define (interact p)
   (let ((child (car p))
  (in (cadr p))
  (out (caddr p)))
     (run (stty raw -echo)) 
     (& (begin (exec-epf (cat) (= 1 ,out))))
     (exec-epf (cat) (= 0 ,in))))
 
 (define-syntax bg
   (syntax-rules ()
     ((_ cmd) 
      (call-with-values 
   (lambda () (fork-pty-session (lambda () (exec-epf cmd))))
        list))))
 
 (define-syntax expect
   (syntax-rules ()
     ((_ cmd proc)
      (let* ((p (bg cmd))
      (in (cadr p)))
        (let l ((b ""))
   (l (string-append (proc p b) (string (read-char in)))))))))
 
 (define (handled m b r)
   (let ((e (+ m (string-length r))))
     (display (substring b 0 e))
     (substring b e (string-length b))))
 
 (define-syntax expect-cond
   (syntax-rules (=>)
     ((_ b (r => a ...) c ...)
      (let ((m (string-contains b r)))
        (if m
     (begin a ... (handled m b r))
     (expect-cond b c ...))))
     ((_ b) b)))
 
 (expect 
  (.. cmd ..)
  (lambda (p b)
    (let ((po (caddr p)))
      (expect-cond
       b
       ("assword: " => (display "pwpw\n" po))))))