This explanation of how %r works here is incorrect: > I knew about `%r` but hadn't realized that it escapes forward-slashes while leaving other regex symbols i

This explanation of how %r works here is incorrect: > I knew about `%r` but hadn't realized that it escapes forward-slashes while leaving other regex symbols intact. The correct explanation can also be found in the next sentence of your comment: > But with the previous explanation of `%q`, in which arbitrary delimiters can be used, it makes sense...curly braces simply replace `/` as the delimiter, and `/` simply retains its non-specialness in regex.