Easiness on the eye of lua-rx, unfortunately, comes with a price: it is a macro and it is expanded for each invocation unless the function is compiled, so performance-wise regexp construction should take place at module level.

Also, I've given this a long stare and it seems that since `cont-bol` (`cont-eol`) regexp already ensures that continuation tokens are not followed (preceded for `cont-eol`) by `lua-operator-class` characters, you could probably replace the whole "override" sections with simply adding `:` to `lua-operator-class` variable.