snippet.rb

# Uses Ruby 1.9 syntax for lambdas
counter = -> initial do 
  val = initial
  foo = {next: -> {val += 1}, reset: -> {val = initial}}
  def foo.method_missing(meth, *args)
    self[meth].call
  end
  foo
end
c = counter.(10)
p c.next   #=> 11
p c.next   #=> 12
p c.reset  #=> 10