Regex error

[Puzzle2011]

I am trying to validate that the user has entered their phone number in this format (555) 555-5555. I keep getting this error: Unmatched ) in regex; marked by <-- HERE in m/[([0-9]) <-- HERE ]+[[0-9]-]+[[0-9]+/ at validate.cgi line 46. My code is below. Any help?

sub validate_input {
my $valid = "Y";
my $errormsg;
if ($phone !~ m/[([0-9])]+[[0-9]-]+[[0-9]+/]) {
$valid = "N";
my $errormsg = "enter a valid phone number in format desired.";
}
return $valid, $errormsg;
}

[tpflicke · Accepted solution]

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.