Doesn't this go against the "literals are enclosed in quotes" idea? In this case, you have a special character (`-`) inside a quoted string. IMO this would be more consistent: `['0'-'9''a'-'f'']`, maybe even have comma separation like `['0'-'9','a'-'f'']`. This would also allow you to include the character classes like `[d,'a'-'f'']` although that might be a little confusing if you're used to normal regex.
> Doesn't this go against the "literals are enclosed in quotes" idea?
Sure, one could argue that other changes would also be useful, but then it would be less concise. I think the main reasons why people like regex are: (a) powerful, (b) concise.
For my V2 proposal, the new rule is: "literals are enclosed in quotes", the rule isn't "_only_ literals are enclosed in quotes" :-) In this case, I think `-` can be quoted as well. I wanted to keep the v2 syntax as close as possible to the existing syntax.