OK, I figured it out, it's in the `magit--cherry-move' function:

--8<---------------cut here---------------start------------->8---
                   (push (format "%s=perl -i -ne '/^pick (%s)/ or print'"
                                 "GIT_SEQUENCE_EDITOR"
                                 (mapconcat #'magit-rev-abbrev commits "|"))
                         process-environment)
--8<---------------cut here---------------end--------------->8---

This "perl" could not be automatically detected by the Guix path-patchers.

We could patch this but I think this also deserves an upstream fix:

	https://github.com/magit/magit/issues/3537

-- 
Pierre Neidhardt