Learning Ruby - class

#!/usr/env/ruby

class Dog
    FORMAT = 'we have %d dogs.'
    @@num = 0

    class << self
        def count
            sprintf(FORMAT, @@num)
        end
    end

    def initialize(name)
        @name = name
        @@num += 1
    end

    def say
        'I am ' << @name
    end
end

puts Dog.new('pochi').say
puts Dog.new('chalo').say

p Dog.count