Numerical variables in pqsql statements

Folks,
I'm sure this is dumb, but I'm a little confused about use of numerical variables in pqsql. It was my impression one had to use EXECUTE on a concatenated string including quote_literal() for the variable containing the value. This can be quite a bit of trouble. I just wrote a function that included the statement :

CREATE TEMPORARY TABLE author_names AS
SELECT ra.ref_auth_key, a.last_name, a.first_name
FROM ref_auth ra INNER JOIN authors a
ON (ra.author_num = a.author_key)
WHERE ra.ref_num = refer_num;

where refer_num is integer. This worked (surprisingly, to me). So, what is the rule regarding variables? Would this query work if I concatenated a string together, including quote_literal(refer_num) and then EXECUTEd it?

Thanks and sorry to be so stupid.