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Adding lookbehinds to the regexp library is a terrible idea.

> The regexp implementation provided by this package is guaranteed to run in time linear in the size of the input.

Python's is exponential, because it inherits all the non-regular "regular" expression mess (such as lookbehind and backrefs) from perl.

One would assume esr would have marinated in unix culture for long enough to be aware of this.

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Some projects need performant regexes, and some honestly just don't. I agree that keeping the base regex library linear is admirable, but it's be nice if they offered a well-marked thing like regex.slow_and_perl_like in the stdlib

https://godoc.org/github.com/glenn-brown/golang-pkg-pcre/src...

This would contravene the training-wheels nature of Go.

Also, Perl-style (ir-)regular expressions, despite their popularity, are not a worthwhile abstraction IMO and thus should not be enshrined in the standard library of programming languages, even if you want them in your library eco-system for end-user facing API compatibility.

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