DirtyTrackingArray.rb

class DirtyTrackingArray < Array
  attr_accessor :dirty
  
  def initialize
    @dirty = false
  end
  
  def push(value)
    @dirty = true
    super
  end

  def <<(value)
    @dirty = true
    super
  end
end

x = DirtyTrackingArray.new
puts x.dirty
x.push 'foo'
puts x.dirty
x << 'bar'
puts x.dirty
puts x.inspect