$ cat foo.scm
(define (foo bar)
  (_ "boom")

$ xgettext --omit-header -L Scheme --keyword=_ -o foo.po foo.scm

$ cat foo.po 
#: foo.scm:2
msgid "boom"
msgstr ""


;;;
;;; Now with DSSSL
;;;

$ rm foo.po

$ cat foo.scm
(define (foo #!key bar)
  (_ "boom")

$ xgettext --omit-header -L Scheme --keyword=_ -o foo.po foo.scm

$ cat foo.po
cat: foo.po: No such file or directory