(Credit card # validation regular expression)
The regex \b(?:\d[ -]*?){13,16}\b is a powerful tool used for validating credit card numbers. Credit card numbers typically consist of a sequence of 13 to 16 digits,
with optional spaces or dashes in between. This regular expression applies the Luhn algorithm to ensure the validity of credit card numbers by checking for the correct number of
digits and the proper formatting. By using this regular expression, developers can easily implement credit card number validation in their applications, helping to enhance security
and prevent errors during data entry.