sample_use.sql

CREATE FUNCTION pltestlang_call_handler() RETURNS language_handler
    AS 'filename'
    LANGUAGE C;
CREATE LANGUAGE pltestlang
    HANDLER pltestlang_call_handler;

CREATE OR REPLACE FUNCTION sum_ints(integer, integer)
  RETURNS integer AS
$BODY$
BEGIN
foo bar baz
END;
$BODY$
LANGUAGE 'pltestlang';

SELECT * FROM sum_ints(4, 6);