scheme@(guile-user)> (sleep/1)
^Cice-9/boot-9.scm:1669:16: In procedure raise-exception:
User interrupt

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(guile-user) [1]> ,bt
In system/repl/repl.scm:
   159:22  4 (_)
In ice-9/boot-9.scm:
   2170:4  3 (%start-stack _ _)
In unknown file:
While executing meta-command:
In procedure frame-local-ref: Argument 2 out of range: 0
scheme@(guile-user) [1]>