With a default Ubuntu 10.04 on VPS.net I have found that when running perl scripts the following warning is shown.

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LANG = "en_GB.utf8"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

After a bit of Googling I found the simple solution to be to do

sudo apt-get install language-pack-en

also I would recommend doing

sudo update-locale

which solves another locale issue.