gistfile1.rb

class ContactDetails
  def initialize
    @hash = Hash.new{ |h,k| h[k] = Array.new }
  end

  def history(key)
    @hash[key]
  end

  def method_missing(method_name, *args, &block)
    method_name = method_name.to_s
    setter = method_name.chomp!('=')
    
    if setter
      @hash[method_name].delete(args.first)
      @hash[method_name].unshift(args.first)
    else
      @hash[method_name].first
    end
  end
end

contact_details = ContactDetails.new
contact_details.work_phone = '011 123 4567'
contact_details.work_phone = '011 765 4321'
contact_details.work_phone #=> 011 765 4321
contact_details.history('work_phone') #=> ['011 765 4321', '011 123 4567']