default database selector

I am running Ubuntu 11.04, I have Postgres 8.4 and 9.1 installed.

My default when I say psql it connects to postgres 8.4

ie I set export PGCLUSTER=9.1/main

it connects to 9.1

Q.  How can I connect to 9.1 by default without having to set PGCLUSTER?

I looked in /etc/postgresql-common, there did not seem to be anything
obivious in there for which version to use.

Dave.
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