def require_relative(relative_feature)
  c = caller.first
  e = c.rindex(/:\d+:in /)
  file = $`
  if /\A\((.*)\)/ =~ file # eval, etc.
    raise LoadError, "require_relative is called in #{$1}"
  end
  absolute_feature = File.expand_path(File.join(File.dirname(file), relative_feature))
  require absolute_feature
end