Digit check and formatting on Brazilian Individual Taxpayer Registry (CPF).
using CpfLibrary;
Cpf.Check("29594421134"); // True
Cpf.Check("488.081.131-91"); // True
Cpf.Check("00000000000"); // False
Cpf.Check("lol"); // False
Cpf.Format("29594421134"); // "295.944.211-34"
Cpf.Format("lol"); // "lol"