$ wget http://parenteses.org/mario/misc/weirdness.tar.gz
$ tar xzf weirdness.tar.gz
$ cd weirdness/
$ chicken-install free-gettext  # in case you don't have it installed

$ cat weirdness.scm 
(use free-gettext)

(define language (make-parameter "pt_BR"))

(print "language: " (language))

((make-gettext "foo" (language) "foo/locale")
 'getter)

(print "language: " (language))


;;;
;;; Note the change of case of "pt_BR".  Why?
;;;


$ csi -s weirdness.scm 
language: pt_BR
language: pt_br

$ mv foo/locale/pt_BR/LC_MESSAGES/foo.mo foo/locale/pt_BR/LC_MESSAGES/foo.mo_
$ csi -s weirdness.scm 
language: pt_BR
language: pt_BR

$ mv foo/locale/pt_BR/LC_MESSAGES/foo.mo_ foo/locale/pt_BR/LC_MESSAGES/foo.mo

$ csi -s weirdness.scm 
language: pt_BR
language: pt_br