这是什么意思?

为什么有些shell运行就会出现这样的问题,怎样可以避免呢?
perl: warning: Setting locale failed.
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").