Use something other than `$` for capture group prefix

[nc7s]

$ is good in programming languages, but interacts badly with shells. Disambiguation of numbered capture groups goes even further, as ${} is also a shell construct.

% might be a good choice.

[butter-radish]

What’s wrong with backslashes, like ‘sed’?

[nc7s]

What’s wrong with backslashes, like ‘sed’?

It's the start of escape sequences, and I can never remember what exactly are escaped and how, so tend to avoid it.