fix for bug in "metaprogramming ruby" book code snippet on page 121 (creating DSL). It calls events of previous files again for each new file loaded and redflag2.rb is another way creating it.

redflag.rb

lambda {
setups = []
events = {}

Kernel.send :define_method, :event do |name, &block|
 events[name] = block
end

Kernel.send :define_method, :setup do |&block|
setups << block
end

Kernel.send :define_method, :each_event do |&block|
events.each_pair do |name, event|
block.call name, event
end
end

Kernel.send :define_method, :each_setup do |&block|
setups.each do |setup|
block.call setup
end
end
}.call

Dir.glob('*event*.rb').each do |file|
load file
end
each_event do |name, event|
env = Object.new
each_setup do |setup|
env.instance_eval &setup
end
 puts "ALERT #{name}" if env.instance_eval &event 
end

redflag2.rb

lambda {
event = {}
setup = []
 Object.class_eval do 
  define_method :event do |name,&block|
   event[name]=block
  end	
 end
 
 Object.class_eval do
   define_method :setup do |&block|
    setup << block
   end
 end
  
Dir.glob('*event*.rb').each do |file|
 event={}
 setup=[]
 puts "====>>>found #{file}"
 load file
event.each_pair do |eventName,eventy|
 puts "---setting clean room for--------->#{eventName}"
 o=Object.new
 setup.each do |block|
  o.instance_eval &block
 end
 puts "ALERT #{eventName}" if o.instance_eval &eventy 
end
end
}.call