[h-cobordism]

You're referring to raw string literals, right?

[steveklabnik]

Yes. You need to include more #s than you have in the string, and it’s rare to have a ton of them, let alone a raw string literal in the first place.

[wtetzner]

Does that make the grammar context-sensitive, or just the lexer?

[steveklabnik]

This is not an area of my expertise, so I can't say.