class Integer
	def random_string
		(1..self).collect { (i = Kernel.rand(62); i += ((i < 10) ? 48 : ((i < 36) ? 55 : 61 ))).chr }.join
	end
end

class Module
	def wrap method, &block
		term = "_" + 5.random_string
		unless method_defined? "#{method}#{term}"
			alias_method "#{method}#{term}", method
		else
			return override(method, &block)
		end
		define_method(method) do |*args|
			begin
				block[*args]
			rescue
				self.send("#{method}#{term}", *args)
			end
		end
		public(method)
	end
end

class File
	wrap(:atime) do |*args|
		raise "Blah" unless args[0] == 0
		42
	end

	wrap(:atime) do |*args|
		raise "Blah" unless args[0] == 1
		nil
	end
end

File.new("a").atime                                # => Wed Oct 18 15:23:36 PDT 2006
File.new("a").atime(0)                             # => 42
File.new("a").atime(0) == 42                       # => true
File.new("a").atime(1)                             # => nil
!File.new("a").atime(1)                            # => true