Function problem again...

Hello,
I hope this is a quick question, I want to create a function that will take a
number of varchars as input .
If it was a single varchar as input i know it would be

CREATE FUNCTION "user_id_funct_p3" (varchar) RETURNS varchar AS '

and if it is multiple I think it would be

CREATE FUNCTION "user_id_funct_p3" (varchar varchar varchar) RETURNS varchar
AS '

however i the number of inputs are not going to be constant do I have to
generate the function every time.. with the right number of inputs or is
there a way to tell a function that the input will be setof varchar

I hope I am making sense

Thanks in advance

Mole