Larry spricht:

On the other hand, if we make people declare their weird brackets,
then they could use the many So (symbolic other) symbols that aren't
officially Ps/Pe pairs, but can easily be used that way, such as
WHITE RIGHT POINTING INDEX and WHITE LEFT POINTING INDEX.

Down that path lies jollity.
             -- Larry Wall in <199911021845.KAA01167@kiev.wall.org>