>>717 (info "(elisp)Regexp Backslash") | `\cC' | matches any character whose category is C. Here C is a character | that represents a category: thus, `c' for Chinese characters or | `g' for Greek characters in the standard category table.
というのがあるんだけど、C の説明が無いね。 \cj だった気がするけど、不具合があるかもしれん。
ASCII 以外だと、↓これはいかが? (info "(elisp)Char Classes") | `[:multibyte:]' | This matches any multibyte character (*note Text | Representations::).