Ironic, from the authors of RE2. They know the correct way to implement regexes.
Though, when I worked on Google's indexing system, some researchers were having machine learning generate regexes to run on every page in the visible web... and mis-implemented the feature to re-compile the regex to DFA (which re2 effectively lazily converts to NFA via memoization) for every single page load. The speed of the indexing system dropped in half one day, and dug into it. took the gperf graph showing the giant node for regex compilation and wrote a savage meme "Your mother doesn't work here. Optimize your own code.", and sent it out to the researchers in question and also the indexing team. Maybe 6 months earlier, I cut into the same researchers for writing and approving C++ header file changes that defined (and leaked) macros "DO" for "{" and "OD" for "}" so that they could write C++ a bit more like Bash. As I remember, the macro leak for DO caused compilation errors in SpiderMonkey, which I fixed. After fixing the breakage, I just left an extra comment on the code review "Really? Leaking DO and OD macros to avoid typing curly braces?" without emailing any lists. They were really embarrassed removed DO and OD within a couple of days, and didn't know that I had laid into them a bit 6 months earlier.
(I had implemented some very coarse-grained super-lightweight
type-based data flow analysis into SpiderMonkey, which is why some of the Google headers were being included while compiling SpiderMonkey.)