>>650
class String
　 def indices(arg, &block)
　 　 pos = 0
　 　 setter = eval("proc{|m|$~=m}", block)
　 　 while (pos = index(arg, pos)) do
　 　 　 setter.call($~)
　 　 　 yield pos
　 　 　 pos += 1
　 　 end
　 end
end