The characters ( and ) in regex are used for grouping so you need to escape them if you want to match literally. You can also use \d for digit, I find it more readable than [0-9]. Try m/\(\d\d\d\)\s*\d\d\d-\d\d\d\d/ m/\(\d{3}\)\s*\d{3}-\d{4}/ m/\(\d+\)\s*\d+-\d+/ depending on whether you want to exactly match the number of digits and preference of style. ... View more