Is splitting at newlines really your bottleneck? Or are you microoptimizing irrelevant parts of your code?

Try Devel::NYTProf, generate a report (run nytprofhtml) and look for code that is highlighted in red, because it is slow or runs very often. That's where you want to optimize for speed. (See also https://www.slideshare.net/Tim.Bunce/nyt-prof-201406key) Everything else should be optimized for maintainance, i.e. keep your code clear, readable, and documented.

Alexander