A little over two weeks, I was having a problem with a server, it always showed me the error:

 perl: warning: Setting locale failed.
perl: warning: Please check your que locale settings:
LANGUAGE = "en_US",
LC_ALL = (unset),
LC_MESSAGES = "en_US.UTF-8"
LC_COLLATE = "en_US.UTF-8"
LC_CTYPE = "en_US.UTF-8"
LANG = "en_US.UTF-8"
are supported and installed on your system. 

And finally found the solution. The error did not cause or problem use, but fumbled the display on the terminal. (Imagine how cool it was when I accessed by phone.

Resolution

First define the variables of the system for the language you wanted.

 export LANGUAGE = en_US.UTF-8
export LANG = en_US.UTF-8
export LC_ALL = en_US.UTF-8 

After we generate the desired language file:

 locale-gen en_US.UTF-8 

And finally reconfigure the locales package:
Locales

 dpkg-reconfigure 

If the error continues send reinstall the package locales:

 apt-get install locales-reinstall 

One solution, very, very, very easy. But I had a great difficulty, for most forums and tutorials that I thought, just tell me the last two steps.

Update on October 26, 2012:

To facilitate scriptque is only created a run, and ready ta repaired. locales.sh