gistfile1.rb

$stdin.read.lines.each do |line|
  number = line.strip
  luhn = line.strip.chars.to_a.reverse.each_with_index.map do |v,i|
    val = v.to_i
    if (i - 1) % 2 == 0
      (val * 2).to_s.each_char.reduce(0) { |memo,n| memo + n.to_i }
    else
      val
    end
  end.reduce(&:+)
  valid = "FALSE"
  valid = "TRUE" if luhn % 10 == 0 && ["51", "52", "53", "54", "55", "4"].any? { |s| number.start_with?(s) }
  puts "#{number},#{valid}"
end