Regardless of which one is more efficient, I wonder why you even care. You've already taken the decision to use Perl instead of, say C, and taken an gigantic efficiency hit. Once gone that way, care about using efficient algorithms. Don't do silly things which you think may save you a few microseconds. If those microseconds are important to you, do not use Perl. Perl is very well suited to do many things - but one thing it sucks at is creating the fastest solution to solve a problem. (It may create a solution faster than in C, but not a faster solution).