How do you write a regular expression with optional character * at the end of a TIN?

Question

The regular expression for a TIN is ^\d{3}-\d{2}-\d{4}$, but I need to accept the following (with or without the "*"):

123-45-6789 or 123-45-6789*

Answer 1

Make it match one * (normally a special character, but escaped with the backslash it becomes the literal * character), optionally (with ?, which means 0 or 1 of the previous):

^\d{3}-\d{2}-\d{4}\*?$