using postgres functions for domain tables

[Matthias Leopold]

hi,

i want to use postgres (8.3) plperl functions to provide 
virtual_mailbox_domains/relay_domains.

is this possible?

how do i make a postgres plperl function return a value/row only when 
certain conditions are met and otherwise return "nothing"/void/0 rows? 
right now my function returns "1 row" even when i return undef.

i know this is more of a postgres question, but i couldn't find an 
answer in postgres docs/lists yet. maybe someone here can help me out ;-)

thx
matthias