Receive a record not a tuple - plpgsql

Dear Friends

How can I call a function into a function? My problem is: I'm trying to
calculate a tax(inss) over a employer salary. I created a function
called inss that do it correctly, but when I create another one to show
more attributes (inss is not a attribute, it is calculate over a salary)
I receive a record (like {1,Mary,32.45} not a tuple. How can I solve it?

CREATE TABLE emp
(
cod numeric
name text NOT NULL,
last_date timestamp,
last_user text,
salary numeric,
CONSTRAINT pkey PRIMARY KEY (cod)
)

CREATE FUNCTION inss() RETURNS numeric AS '
SELECT salary*0.11 FROM emp;
'LANGUAGE 'sql';
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It is OK
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CREATE OR REPLACE FUNCTION mostra_inss() RETURNS setof record AS '

select name, inss(), salary from emp;

'LANGUAGE 'sql';
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--- Only for test --- DROP FUNCTION show_inss();
--- Only for test --- select inss();
---------------------------------------------------------------------------------------------
--- Another Test - Not OK

CREATE OR REPLACE FUNCTION show_inss() RETURNS VARCHAR AS '
DECLARE
inss float;
BEGIN
SELECT INTO inss inss() FROM emp;
RETURN inss;
END;
' LANGUAGE 'plpgsql';
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--- Another Test (NOT OK)
---------------------------------------------------------------------------------------------
create or replace function test_inss() returns record as '
DECLARE
d record;
BEGIN
for d in select name,salary,inss() from emp
loop
end loop;
RETURN;
END;
' language 'plpgsql';

select test_inss();