$ csi -s repro2.scm 
before
within

Error: boom

	Call history:

	<syntax>	  (print* "before\n")
	<syntax>	  (lambda () (print* "within\n") (error (quote boom)))
	<syntax>	  (##core#lambda () (print* "within\n") (error (quote boom)))
	<syntax>	  (##core#begin (print* "within\n") (error (quote boom)))
	<syntax>	  (print* "within\n")
	<syntax>	  (error (quote boom))
	<syntax>	  (quote boom)
	<syntax>	  (##core#quote boom)
	<syntax>	  (lambda () (print* "after\n"))
	<syntax>	  (##core#lambda () (print* "after\n"))
	<syntax>	  (##core#begin (print* "after\n"))
	<syntax>	  (print* "after\n")
	<eval>	  (dynamic-wind (lambda () (print* "before\n")) (lambda () (print* "within\n") (error (quote boom))) (...
	<eval>	  (print* "before\n")
	<eval>	  (print* "within\n")
	<eval>	  (error (quote boom))	<--