Hi!

Using the attached foo.scm and bar.scm, Guile 2.2 nicely redefines
%foo and %baz:

--8<---------------cut here---------------start------------->8---
$ guild compile -L . -o foo.go foo.scm
wrote `foo.go'
17:48:10 janneke@dundal:~/src/guile/master [env]
$ guild compile -L . -o bar.go bar.scm
wrote `bar.go'
17:48:12 janneke@dundal:~/src/guile/master [env]
$ guile -C . -c '(use-modules (bar))'
foo: "foo"
baz: "baz"
17:48:16 janneke@dundal:~/src/guile/master [env]
$ guile -C . -c '(use-modules (bar))'
foo: "foo"
baz: "baz"
--8<---------------cut here---------------end--------------->8---

Guile-3.0 sets %foo to *unspecified*:

--8<---------------cut here---------------start------------->8---
$ meta/build-env meta/guild compile -L . -o foo.go foo.scm
wrote `foo.go'
17:50:03 janneke@dundal:~/src/guile/master [env]
$ meta/build-env guild compile -L . -o bar.go bar.scm
wrote `bar.go'
17:50:10 janneke@dundal:~/src/guile/master [env]
$ meta/build-env meta/guile -C . -c '(use-modules (bar))'
foo: #<unspecified>
baz: "baz"
--8<---------------cut here---------------end--------------->8---

Greetings,
Janneke