[mseepgood]

You're looking at the wrong production. They are octal literals:

    octal_lit      = "0" [ "o" | "O" ] [ "_" ] octal_digits .

[Someone]

Thanks! Never considered that a 21st century language designed for “power of two bits per word” hardware would keep that feature from the 1970s, so I never looked at that production.

Are there other modern languages that still have that?