(use posix srfi-18)
(print "begin " (current-milliseconds))
(thread-start! (lambda () (print (with-input-from-pipe "sleep 5 ; echo foo" (lambda ()
                                                                              (thread-wait-for-i/o! (current-input-port))
                                                                              (read-string (current-input-port)))))))
(thread-yield!)

(print "end " (current-milliseconds))