MWE for conflict of listen and parallel gems

parallel-listen.rb

#!/usr/bin/ruby

require 'rubygems'
gem "parallel"
require 'parallel'
gem "listen"
require 'listen'

listener = Listen.to('.') do |modified, added, removed|
  $changetime = Time.now
end
$changetime = Time.now
listener.start

begin
  Parallel.map([1,2,3,4], :finish  => lambda { |a,b,c| puts c }) { |job|
    begin
      # Do something time-consuming
      sleep(2)
      job
    rescue => e
      puts "\tAn error occurred: #{e.to_s}"
      # Should we break? Let's see what kinds of errors we get...
    end
  }
  # Do we have to care about Parallel::DeadWorker?

  # Wait for files to change
  files = Thread.new do
    while ( $changetime <= start_time || Time.now - $changetime < 2 )
      sleep(0.5)
    end

    while ( Thread.current[:raisetarget] == nil ) do end
    Thread.current[:raisetarget].raise(Interrupt.new("Files have changed"))
  end
  files[:raisetarget] = Thread.current
end while ( true )