Oh, I think I see the problem:
8.0 pg_regress:
if [ "$unix_sockets" = no ]; then postmaster_options="$postmaster_options -c listen_addresses=$hostname"
else postmaster_options="$postmaster_options -c listen_addresses=''" fi
8.1 pg_regress:
if [ "$unix_sockets" = no ]; then postmaster_options="$postmaster_options -c listen_addresses=$hostname"
else postmaster_options="$postmaster_options -c listen_addresses=" fi
regards, tom lane