Hi Hauke D,

Your comments are well taken.
I certainly wouldn't say that there is anything wrong at all with using the single regex for trimming the lines.
A large amount of Perl that I write involves processing text files which come from various sources, sometimes cut-n-paste amalgamations generated by users. I can't think of any example where the "line trim" code or "skip blank line" code, e.g. next if /^\s*$/; played any significant performance role at all. Leaving a blank line in the file is so common that I almost always add that fast regex (its fast because of the anchors) to get rid of non-data lines.

Performance can be a very, very application specific thing. I wrote one program that took 4 hours to run. I got complaints as to the run time. I asked, "how many times per year do you run this program?". Answer: 4 times per year. I used algorithms that made it easy for me to develop/debug and track down any questionable decision(s) and also to come as close as I could to guaranteeing that it produced a correct result. Accuracy was my main goal. I never got an answer about why 4 hours mattered. New management ordered it to be recoded, with a goal of much faster at the expense of perhaps a 10% error rate. So the new version runs much faster, but makes more mistakes. Which is better? Depends upon what you want.

Algorithms and data structures make a lot more difference than this simple "what do I do with this single line" although I will admit to beating on a single critical important regex line for an entire week to squeeze some more performance out of it - if you do it a million times, it can matter a lot.