require 'stringio'

module Helpers
  def capture(*streams)
    streams.map!(&:to_s)
    begin
      result = StringIO.new
      streams.each { |stream| eval "$#{stream} = result" }
      yield
    ensure
      streams.each { |stream| eval("$#{stream} = #{stream.upcase}") }
    end
    result.string
  end
end