Comment 1984 added to page plpgsql.html of version 7.4

Author: James Nakasone Wong <janaka_tech(at)bluebottle(dot)com>
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=====================
CREATE FUNCTION somefunc() RETURNS integer AS '
DECLARE
quantity integer := 30;
BEGIN
RAISE NOTICE ''Quantity here is %'', quantity; -- Quantity here is 30
quantity := 50;
--
-- Create a subblock
--
DECLARE
quantity integer := 80;
BEGIN
RAISE NOTICE ''Quantity here is %'', quantity; -- Quantity here is 80
END;

RAISE NOTICE ''Quantity here is %'', quantity; -- Quantity here is 50

RETURN quantity;
END;
' LANGUAGE plpgsql;

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I 've saved above text in f2.sql
then when I upload this file (f2.sql) an error appeared? can anybody advice what shall I need to do from there ?

============================
test=# \i f2.sql
psql:f2.sql:20: ERROR: language "plpgsql" does not exist
HINT: You need to use "createlang" to load the language into the database.
test=#
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