how to improve the performance of a regular expression

It's hard work! If it is important enough for you to spend your time on, (and you're a masocist!), then try enabling use re 'debug';. This will tell you FMTYEWTK, about what is going on inside the regex engine.

As for "Are there heuristics you've learned?", the most basic one is reScriptWithDebug > log & wc -l log. Lower numbers mean "more efficient"!

Essentially, the less log your re generates, the faster it will run (without the logging). Which of course "begs the question", which despite the purist lamentations, I'm going to ask on your behalf. "

How do you know which regex contructs will generate the least logging?

And the answer is: suck it and see. (Paraphrase: benchmark!). But to do that, you need a range of possible candidate regexes that meet your actual needs--as opposed to either your stated needs, or those assumed by the pedants.

Back around the 5.6.1 timeframe, Jeffery Friedl's book, Mastering regular expressions, would give you definitive answers to most regex questions--assuming that you could force yourself to read through, the rather dry, complete works. But, like life, Perl and it's regex engine, moved on. So now, the only way to optimise your regexes, is to benchmark them.

One possible approach is to realise that the looser (more permissive; least specific), the regex, the faster it is likely to run.

Another is to post a "please speed this up" post here at PM. But don your thick skin, cos ~70% of the replies will likely be "Optimisation is the route of all evil", knock offs! Without the proofs. Or understanding.

So, if you have just posted a generic "how to" question, in place of a specific, "I really need to speed up this regex" question, repost the latter. Make it a challenge! Offering mega-qodos.

Incite the competetive nature of the monks. Maybe, just maybe, you'll re-kindle the interest of some of those that used to make this place so much fun, but that have ceased to intereact here, because the pedants and PC-police have driven away those that made this place work in the first place.

The japhys, and dwss and aristotles. Those with whom you could have a technical argument, without personal afront. Those who's ingrained desire to know, supplanted the group-speak invictive for control and conformity.

We can but hope!