Warning: variable $KCODE is no longer effective

ruby-talk
1

This warning comes from accessing $KCODE. What should be used instead?

In particular, this snippet from RDoc:

@charset = case $KCODE
           when /^S/i
             'Shift_JIS'
           when /^E/i
             'EUC-JP'
           else
             'iso-8859-1'
           end

Eventually @charset is placed in a <meta http-equiv> in the output RDoc. Is there a better way to determine the charset of a file?