Comment by IshKebab

They're very quick to write and they (in appropriate cases) would be quite difficult to implement otherwise (tedious state machine stuff). They are still massively overused though. Using a regex at all is a huge red flag. Sometimes they are appropriate, but not in 90% of cases in my experience.

Anyway I'm not sure the same is true for K. At least for the given example the for loop was not exactly difficult to write.