define-language

[Stephen Scheck <singularsyntax@gmail.com>]

What is the right way to use `define-language`? The Guile manual says that
when using this form "the language will be added to the global language
set." I interpret that to mean that the `,language` meta-command switches
the REPL to use the newly-defined language, but it doesn't work:

scheme@(guile-user)> (use-modules (system base language))
scheme@(guile-user)> (define-language mylingua
  #:title "Mylingua"
  #:reader (lambda (port env) ...)
  #:evaluator (lambda (x module) ...)
  #:printer write)
scheme@(guile-user)> mylingua
$1 = #<<language> name: mylingua title: "Mylingua" reader: #<procedure
1bfcd38 at <unknown port>:5:11 (port env)> printer: #<procedure write (_
#:optional _)> parser: #f compilers: () decompilers: () evaluator:
#<procedure 1bfcd48 at <unknown port>:6:14 (x module)> joiner: #f
for-humans?: #t make-default-environment: #<procedure
make-fresh-user-module ()> lowerer: #f analyzer: #f compiler-chooser: #f>
scheme@(guile-user)> ,language mylingua
While executing meta-command:
no such language mylingua