# File lib/rbot/config.rb, line 184
    def add(val)
      newval = self.get.dup
      unless newval.include? val
        newval << val
        validate_item(val) or raise ArgumentError, "invalid item: #{val}"
        validate(newval) or raise ArgumentError, "invalid value: #{newval.to_s}"
        set(newval)
      end
    end