I’ve seen this perl error for a while and ignored it but it was stopping postgres from starting. This is on Ubuntu Intrepid 8.10, specifically a JeOS install made by vm-builder, which is the key.
$ sudo /etc/init.d/postgresql-8.3 start * Starting PostgreSQL 8.3 database server * perl: warning: Setting locale failed. perl: warning: Please check that your locale settings: LANGUAGE = (unset), LC_ALL = (unset), LANG = "en_US.UTF-8" are supported and installed on your system. perl: warning: Falling back to the standard locale ("C"). The PostgreSQL server failed to start. Please check the log output: FATAL: invalid value for parameter "lc_messages": "en_US.UTF-8"
sudo apt-get install language-pack-en