client.rb

class VCR::Client
  def current_cassette
    cassetes.last
  end

  def configure
    yield configuration
  end

  def configuration
    @configuration ||= Configuration.new
  end
  
  private

  def cassettes
    @cassettes ||= []
  end
end

vcr.rb

module VCR
  extend self
  
  delegate :current_cassette, :configure, :configuration, :to => :default_client
  
  def default_client
    @default_client ||= Client.new
  end
end