in reply to
How to use \l and \u in regex mathing patterns?
I certainly don’t find the oblique comment, “Think vi” in perldoc perlre to be particularly informative ... but then again, I don’t regularly use vi. I therefore cordially suggest that I have never used them or paid any attention to them, and I do feel that I am none the worse for wear. I would use character-classes and other such strategies to accomplish the intended result, and studiously avoid these. But, that’s just me, perhaps. I tend to find a way that works and that makes “obvious” sense to me, and that’s the end of it.