Can Naming Rule Expression (Old Style) be configured to include a dot (.) in the result?

Frappe Framework
1

I want to use Naming Rule Expression (Old Style) because I need a series by prefix (separated by a dot).

I want to configure the Naming Rule (Old Style) to include a dot . in the generated name. For example, I would like the result to be something like INV.2025.001. Is this achievable using the old-style expression? If not, what would be the recommended approach?