During my revisited to my vps, I encountered this error:
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LANG = "en_US"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
After googling, I found out that the problem is with the locales being not installed on the system. In order to install it:
% apt-get install locales
% dpkg-reconfigure locales
just choose everything started with en_US, and choose the default as en_US.
That's it, no more locales error message!