banner.rb

class Banner
  def initialize(&block)
    @lines = []
    instance_eval &block
  end

  def line(str)
    @lines << str
  end

  def draw
    puts "=" * 20
    puts @lines.join("\n")
    puts "=" * 20
  end
end

banner = Banner.new do
  line "foo"
  line "bar"
end

banner.draw