Hi, in two threads now you are asking for advice on how to mark matching text substrings with some special marker, by hand, in a very naive way. I suppose you are then going through and looking for the marked substrings to do something else with them.

If you described at a higher level what it is you want to accomplish, the monks could probably provide advice that would get you to your goal in a much simpler way, and coincidentally you'll probably get the optimization you seek.

Perl is the most useful tool set for processing text. It's almost certain that there are modules on CPAN to do what you want. Part of learning to be a programmer is learning which tools already exist and which are best for the job, not always to make a new tool.

Your code as presented could be improved in quite a few ways, but I for one am not inclined to spend time on it since it so obviously is the wrong approach to something. So, care to describe your real task and goal?

( See also XY Problem; Premature Optimization )

Hope this helps!