金額を漢字フォーマットに変換.rb

# -*- coding: utf-8 -*-
numbers = [100, 100000500, 123456789]
numbers.each do |number|
  scales = ["", "万", "億", "兆"]
  puts number.to_s.gsub(/(\d)(?=(\d\d\d\d)+(?!\d))/, "\\1,").split(',').reverse.inject("") {|result, item|
    scale = scales.shift
    item = item.to_i.to_s.gsub(/(\d)(?=(?:\d\d\d)+(?!\d))/, '\1,')
    result = item + scale + result unless item == "0"
    result
  } + '円'
end