plperlu function

Hello

I am an absolute beginner in postgres and apologize in advance for a
possible silly question.
I am running postgreSQL 8.0 on a Suse Linux box

I need to write a function in a postgres database that performs an
extraction on three archives and writes the extracted records in a text
file.
I added the support for the "plperlu" language. I have defined the
function in the following way:

CREATE FUNCTION sampleExtraction() RETURNS boolean AS $$

// function implementation

$$ LANGUAGE plperlu IMMUTABLE STRICT;

I will launch this function manually when needed. My questions are:

- is this feasible in this way ?
- how can I launch/execute the function? Do I need to write a suitable
SELECT or is there an alternative way? Is "SELECT sampleExtraction();"
correct?

Thanks in advance for your kind help

Best regards

Nicola Scioscia