Other regex implementations have escape sequences for horizontal whitespace (`\h` and `\H`) and vertical whitespace (`\v` and `\V`). The regex module already supports `\h`, but I can't use `\v` because it represents `\0x0b', as it does in the re module. Now that someone has asked for it, I'm trying to find a nice way of adding it, and I'm currently thinking that maybe I could use `\y` and `\Y` instead as they look a little like `\v` and `\V`, and, also, vertical whitespace is sort-of in the y-direction. As far as I can tell, only ProgressSQL uses them, and, even then, it's for what everyone else writes as `\b` and `\B`. I want the regex module to remain compatible with the re module, in case they get added there sometime in the future. Opinions?