#!/perl/bin/perl

use strict;
use warnings;

# The assumption is that the number will always be exactly ten digits
my $s = "0123456789";

print $s, "\n";
$s =~ s/^(\d{3})(\d{3})(\d{4})$/($1)$2-$3/;

print $s, "\n";

__OUTPUT__
0123456789
(012)345-6789