Culturally aware initcap

I wrote this little utility function that someone might find useful:

CREATE OR REPLACE FUNCTION cul_initcap(input_val text) RETURNS text AS
$function_body$
-- culturally aware initcap, written by Peter Geoghegan ("sternocera")
-- use this in place of initcap, and strings with possessive
apostrophes are correctly initcap'd
-- (e.g. "PETER'S string" becomes "Peter's String", not "Peter'S String")
-- It still initcaps Irish names like O'Shaughnessy correctly
SELECT regexp_replace(initcap($1), $$'S([^[:upper:][:lower:]]|$)$$,
$$'s\1$$, 'g');

$function_body$
LANGUAGE 'sql' IMMUTABLE;

I'm going to put it on the wiki, because it's a problem that's come up
a good few times on IRC, and it ought to have a template solution.

Regards,
Peter Geoghegan