As you might expect this has come up before.

The classic book to read is Mastering Regular Expressions. For threads that have touched on this see RE (tilly) 4: SAS log scanner and Numeric list to optimised regexp. And for an interesting discussion see also this. Unfortunately I don't think anyone will try to actually implement that in the near future, but you may find it interesting to read.

In reply to Re: Regexp Speed Concerns by tilly
in thread Regexp Speed Concerns by tadman

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