filter.rb

def run_filters(&blk)
  m = Module.new do
    extend self
    @__filter_endpoint = blk
  end
  code = '@__filter_endpoint.call'
  filter_methods = private_methods.grep(/^filter_/)
  filter_methods.each do |meth|
    m.send(:define_method, "__filter_#{meth}", method(meth))
  end
  filter_methods.each do |method|
    code = "send('#{method}') { #{code} } "
  end
  m.module_eval code.tap {|c| puts c}
end

def filter_1
  puts 1
  yield
  puts 1
end

def filter_2
  puts 2
  yield
  puts 2
end

def filter_3
  puts 3
  yield
  puts 3
end

run_filters do
  puts 'core'
end

filter2.rb

def filter(name, &blk)
  @__filters ||= []
  @__filters << [name, blk]
end

def run_filters(&blk)
  @__filter_endpoint = blk
  filter_procs = [proc { @__filter_endpoint.call }]
  @__filters.each do |name, block|
    last = filter_procs.last
    filter_procs << proc { block.call last }
  end
  filter_procs.last.call
end

filter '1' do |app|
  puts 1
  app.call
  puts 1
end

filter '2' do |app|
  puts 2
  app.call
  puts 2
end

filter '3' do |app|
  puts 3
  app.call
  puts 3
end

run_filters do
  puts 'core'
end

filter_fiber.rb

@filters = []
def filter name, &p
  @filters << p
end

def run name, &p
  filters = @filters.map{|f| Fiber.new(&f) }
  filters.each &:resume
  yield
  filters.reverse_each &:resume
end

filter '1' do
  puts '1('
  Fiber.yield
  puts ')1'
end

filter '2' do
  puts '2('
  Fiber.yield
  puts ')2'
end

run '3' do
  puts '3()3'
end