[[ foo =~ pat ]] parsing doesn't match bash and zsh

[andychu]

Details of bash source code here

https://oilshell.zulipchat.com/#narrow/stream/307442-nix/topic/Expected.20.29.2C.20got.20word.2ECompound

Hit by Nix

[andychu]

Released - https://www.oilshell.org/blog/2024/06/release-0.22.0.html