perl: warning: Setting locale failed

[Erik van der Meulen <e.van.der.meulen@avondel.nl>]

Kind all - I seem to be missing some vital setting in my system. When I
start some application from the command line, I get these messages:

  perl: warning: Setting locale failed.
  perl: warning: Please check that your locale settings:
  	LANGUAGE = (unset),
	LC_ALL = (unset),
	LC_CTYPE = "",
	LANG = "en.ISO-8859-1"
      are supported and installed on your system.
  perl: warning: Falling back to the standard locale ("C").

Can someone point me to a fix for this? 

Thanks a lot.

--
  Erik van der Meulen <e.van.der.meulen@avondel.nl>