extlib-hook-after.rb

require 'rubygems'
require 'extlib'

class Foo
  include Extlib::Hook

  def foo(arg)
    p [:foo, arg]
  end

  before(:foo) do |arg|
    p [:before, arg]
  end

  after(:foo) do |arg|
    p [:after, arg]
  end
end

Foo.new.foo(1)

__END__

[:before, 1]
[:foo, 1]
test.rb:21: warning: multiple values for a block parameter (2 for 1)
        from /usr/lib/ruby/gems/1.8/gems/extlib-0.9.14/lib/extlib/hook.rb:253
[:after, [nil, 1]]