Return types of a function

Hi!
I have postgres installed in my machine and have a simple task to do.
Step1) Fetch all the tables in the Database with name staerting with "AA"
Step2) On each table you get fire a simple SQL query:
select * from <tablename>;
Step3) Right these into a flat file.
I have to carry out all these steps using a prcedure/function.

The function would be called by a trigger. Now i need to know how to make a postgres function for that.

My problem: My experience with database is almost 5 days and I can't seem to understand the documentation, like how to catch the return value. How to run the procedure for testing without firing the trigger. So could anyone help me with that.

Regards,
Nalin.