Thanks for writing up the new SRFI Amirouche.

One obvious use for hooks would be customizing the Scheme REPL (e.g.
displaying a custom prompt). John has some sketching along these lines
(search for documents named "repl" at
<https://bitbucket.org/cowan/r7rs-wg1-infra/src/default/>) but I didn't
find anything about hooks yet.