gistfile1.builder

class Foo
  def initialize(counter)
    @counter = 0
    instance_eval "def #{counter}; @counter; end"
  end

  def call
    @counter += 1
    yield
  end
end

a = Foo.new(:foo)

a.call { puts "hi" }
a.foo

a.call { puts "hi" }
a.foo

a.call { puts "hi" }
a.foo