Regex 'Absent Operator'

[Scott Morgan <blumf@...>]

Apparently Ruby's new release has added a new 'absent operator' to it's
regex engine.

https://medium.com/rubyinside/the-new-absent-operator-in-ruby-s-regular-expressions-7c3ef6cd0b99

Based on some academic paper (linked in article, but in Japanese), it's
supposed to help in certain cases matching things that are awkward or
impossible without (C style comments '/* ... */' is one example[0]).
It's a bit subtle in it's behaviour and uses.

Worth considering for Lua's pattern match system?

Scott

[0] That is '/* okay */' but avoiding '/* wrong */ */'