    # File lib/rbot/maskdb.rb, line 77
          def find_helper(*prefs)
            str = prefs.shift or raise 'empty prefs?'
            return [] unless @pre.empty? or str.index(@pre) == 0
            # puts "#{self.inspect}: #{str} == #{@pre} pfx matched"
            if !@chi.include? ''
              matches = []
            elsif Array === @chi['']
              matches = @chi['']
            else
              matches = @chi[''].find(*prefs)
            end

            c = str.slice(@pre.size)

            more = []
            if c and @chi.include?(c)
              more = @chi[c].find_helper(str.slice((@pre.size + 1) .. -1), *prefs)
            end
            return more + matches
          end