global variables in plpgsql?

Folks,

In v8.0.3 documentation, plperl, plpython and pltcl allow declaration of
variables that are global and persistent within a session.

begin_quote
37.4. Global Values in PL/Perl
You can use the global hash %_SHARED to store data, including code references,
between function calls for the lifetime of the current session.
end_quote

So, a couple of questions....
1) Can you declare global values from plpgsql?
2) If so, is there a way of avoiding namespace pollution?  (perhaps the equivalent to Oracle's use of plsql package
variables)

tia
-- 
David T. Bath
dave.bath@unix.net