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> > Nonetheless, every popular programming language (except Go[1])

> ... and Rust. Although Rust doesn't have a regex library in std, the official regex crate (I am its author) descends from RE2[1].

... and Tcl (see my earlier post). You might argue that Tcl is not popular but it still has a significant following.

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I'm not a Tcl expert, but now that I think about it, I'm not sure you're correct. My recollection is that Tcl is one of the few to have a true hybrid engine. So if you use look-around or backreferences, then Tcl could provide an exponential runtime. If that's true, then Tcl would be included in "Nonetheless, every popular programming language (except Go[1]) has included an exponential backtracking regex implementation in their standard library," with perhaps a caveat or special mention. But it's still a categorically different guarantee than what, say, RE2 provides.

... sure. I don't personally consider Tcl to be popular at present though.

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