I remember reading something along these lines in Programming Perl, 2nd edition. It was in a section near the end that listed tips on optimization. (I'm not saying the book was wrong, maybe it was just worded in a way that led me to the same misunderstanding as lokiloki.)

... I just looked at the 3rd edition in my safari bookshelf, and I see that it's chapter 24.2, Efficiency, that I'm thinking of -- but I don't see anything about quoting in this current edition.

Joe