(use srfi-18)

(thread-start! (lambda () (let lp () (print "beep") (thread-sleep! 1) (lp))))

(let loop ()
  (loop))

;;

➜  ~ csi -s asdf.scm
beep
beep
asdfbeep

beep
asdfasdfbeep
asd 
beep
asdf
beep
^C
*** user interrupt ***