books on pl/pgsql

First off, thanks to all for the tips
for trying to do a bit of Pl/Pgsql
programming.

I really don't like to start asking
the group questions about Pl/Pgsql without
at least some research, is there a good
books about Pl/Pgsql out there for
beginners?

I'm really trying to get tips and examples
(especially examples) in the following:

* defining a variable
* using if-then-else statements
(i'm getting errors now ... syntax i think)
* using the exception (or, is it raised exception?)
* execute sql statements within the BEGIN / END block

I'm really trying to do more work without
having to create a bunch of functions.
I only have the 'Postgres: Introduction and
Concepts' book and an 'Oracle 8i: Beginners
Guide' to help me. Both aren't very good at
what I'm looking for.

Suggestions? TIA!

-X