<<TableOfContents()>>

= Cause =
On linux systems, when the enviroment variables refer to locales that haven't been installed locally, a vague perl error can be thrown in some instance:

{{{
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
	LANGUAGE = "en_US:en",
	LC_ALL = (unset),
	LC_ADDRESS = "nl_NL.UTF-8",
	LC_NAME = "nl_NL.UTF-8",
	LC_MONETARY = "nl_NL.UTF-8",
	LC_PAPER = "nl_NL.UTF-8",
	LC_IDENTIFICATION = "nl_NL.UTF-8",
	LC_TELEPHONE = "nl_NL.UTF-8",
	LC_MEASUREMENT = "nl_NL.UTF-8",
	LC_TIME = "nl_NL.UTF-8",
	LC_NUMERIC = "nl_NL.UTF-8",
	LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8")
}}}
= Solution =

 * Run the `export` command, to check what your locale settings are. Look for lines that look like this:
{{{
declare -x LANG="en_US.UTF-8"
declare -x LANGUAGE="en_US:en"
declare -x LC_ADDRESS="nl_NL.UTF-8"
declare -x LC_IDENTIFICATION="nl_NL.UTF-8"
declare -x LC_MEASUREMENT="nl_NL.UTF-8"
declare -x LC_MONETARY="nl_NL.UTF-8"
declare -x LC_NAME="nl_NL.UTF-8"
declare -x LC_NUMERIC="nl_NL.UTF-8"
declare -x LC_PAPER="nl_NL.UTF-8"
declare -x LC_TELEPHONE="nl_NL.UTF-8"
declare -x LC_TIME="nl_NL.UTF-8"
}}}
In this case, nl_NL.UTF-8 is the problem
 * Edit `/etc/locale.gen` an  uncomment the locales referred in your enviroment variables
 * Run `sudo locale-gen` to generate any new locales
Now the problem should be resolved.