Simple colorizer of tests output: given test program printing true or false for test passing, it paints "true" green and "false" red

truecolor.rb

#!/usr/bin/env ruby
# Usage example: echo 'use "hw1test.sml";' | sml | truecolor.rb

require 'colorize'

# HA HA HA I USE GLOBAL VARIABLES
$failed = 0
$passed = 0

while line = gets
  puts(
    line.gsub('true') do |s|
      $passed+=1
      s.green
    end.gsub(/false|<hidden-value>/) do |s|
      $failed+=1
      s.red
    end
  )
end
puts "#$passed passed".green + if $failed > 0 then ", "+"#$failed failed".red else "" end