How to Declare Functions Containing OUT PArameters?

I'm having some difficulty getting plpgsql to recognize a function with
a couple of OUT parameters. I'm either declaring the function
incorrectly, making the call to it in the wrong way or my program is
simply possessed by evil spirits. I'm using Postgres 8.1.5.
What appears to be happening is that it's declaring the function as if
it returned a record and had only two parameters, but I'm trying to
call it with four parameters, with two of them being OUT parameters. So
the compiler sees two different versions of the function and refused to
do anything more. The example below shows the problem, but it's just
something to exercise the function calls and generate the error. Can
anyone spot the screw-up in this little example? (the error message is
listed below in the block comment)
TIA,
-Bill Thoen

CREATE OR REPLACE FUNCTION fishy( s1 text, s2 text, OUT n integer, OUT f
real ) AS $$
DECLARE
c integer;
BEGIN
c := length( s1 );
n := length( s1 || s2 );
f := c::real / n::real;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION main() RETURNS VOID AS $$
DECLARE
str1 text;
str2 text;
num integer := 0;
fnum real := 0.0;
BEGIN
str1 := 'One fish, two fish';
str2 := 'Shark fish, No fish';
SELECT fishy( str1, str2, num, fnum) ;

RAISE NOTICE 'fishy() analysis: % %', num, fnum;
END;
$$ LANGUAGE plpgsql;

SELECT main();

/* ERROR MESSAGE

psql:ex_out_fail.sql:28: ERROR: function fishy(text, text, integer,
real) does not exist
HINT: No function matches the given name and argument types. You may
need to add explicit type casts.
CONTEXT: SQL statement "SELECT fishy( $1 , $2 , $3 , $4 )"
PL/pgSQL function "main" line 9 at SQL statement

And when I run \df from the pgsql command line, it shows up like this:
| fishy | record | text, text

*/