database name aliases?

I'd like to be able to have several versions of a database available concurrently and one database alias that refers to the most recent of these.  For example:

dbname_1-1
dbname_1-2
dbname_1-3
dbname -> dbname_1-3

and
$ psql -d dbname
would connect to dbname_1-3.

Any ideas?

Thanks,
Reece

-- Reece Hart, http://harts.net/reece/, GPG:0x25EC91A0