perl: warning: Falling back to the standard locale (“C”)

Every time I debootstrap a new Debian server for a XenU domain, I get lots of verbose output from Perl scripts:

perl: warning: Setting locale failed.                                      
perl: warning: Please check that your locale settings:                     
        LANGUAGE = (unset),                                                
        LC_ALL = (unset),                                                  
        LANG = "en_IE.UTF-8"                                               
    are supported and installed on your system.                            
perl: warning: Falling back to the standard locale ("C").    

The fix is simple:

# apt-get install locales
# dpkg-reconfigure locales

and select your locales.