$ csi #;3> (use srfi-18) #;4> (thread-start! (lambda () (let loop () (print "hey") (thread-sleep! 1) (loop)))) # #;5> hey hey hey (hey ; 30 seconds later ) Error: illegal non-atomic object: () #;5> hey hey hey [klm@kth ~]$ csi -version CHICKEN (c)2008-2012 The Chicken Team (c)2000-2007 Felix L. Winkelmann Version 4.8.1 (rev e5ed396) linux-unix-gnu-x86-64 [ 64bit manyargs dload ptables ] compiled 2012-09-30 on kth (Linux) [klm@kth ~]$ uname -a Linux kth 3.7.3-1-ARCH #1 SMP PREEMPT Thu Jan 17 18:52:30 CET 2013 x86_64 GNU/Linux