Dir.glob('*.{mp3,MP3}') do |file|
  match = file.match(/^(.+\()(\d+)(\).+)/)
  if (match == nil)
    puts "skipping #{file}"
    next
  end
  front, num, back = match.captures
  num = num.rjust(2, '0')
  newfile = front + num + back
  puts "renaming  #{file}  to  #{newfile}"
  File.rename(file, newfile)
end