As an optimization, you can get a faster pattern match by not putting your spaces into character classes. That just slows the engine down.

You're correct. However, there is not enough information from the OP to determine if that's a good idea.

Someone recently estimated to me in a BOTE calculation that [ ] is 10x slower. That is, this hamstrings the screamingly fast boyer-moore literal string matching part of the regex engine and compiles /xxx[ ]xxx/ down to exact("xxx"), anyof(" "), exact("xxx") where it was originally exact( "xxx xxx" ).

You've changed the regex from one for a seven character literal to one that contains two three character literals. That changes how the engine matches and it changes how quickly the BM part of the engine can either discard entirely or find suitable candidates. It also causes more overhead because three ops have to be executed instead of just one.

I'm asserting that [ ] is pretty to look at but has serious consequences to the regexp's performance. I wouldn't ordinarilly choose the pretty version in that case. I rarely ever use /x though so I don't need to escape my spaces.

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My mistake. I mentally transferred Grandfather's \s+ into the OP, instead of registering the OP's [ ], causing you consternation and me a red face.

My apologies.

BTW, what's a "BOTE"?

-QM
--
Quantum Mechanics: The dreams stuff is made of