Here's the code I tested ...

use strict;

my @p = (
         '(555) 324-1233',
         '555 - 324-1234',
         '555 - 324-1234x204',
         '1 555 342 1234',
        );

my $re = qr/(?:1\s*)?\(?(\d{3})\)?\s*-?\s*(\d{3})[\s-]?(\d{4})(?:x(\d+
+))?/;

for my $p (@p)
{
    if ($p =~ $re)
    {
        printf
            "phone number = %s\n" .
            "area code = %s\n" .
            "exchange  = %s\n" .
            "number    = %s\n" .
            "extention = %s\n",
            $p, $1, $2, $3, $4 ? $4 : 'none';
    }
    else
    {
        print "[$p] doesn't look like a phone number to me\n";
    }
}
[download]

Output:

phone number = (555) 324-1233
area code = 555
exchange  = 324
number    = 1233
extention = none
phone number = 555 - 324-1234
area code = 555
exchange  = 324
number    = 1234
extention = none
phone number = 555 - 324-1234x204
area code = 555
exchange  = 324
number    = 1234
extention = 204
phone number = 1 555 342 1234
area code = 555
exchange  = 342
number    = 1234
extention = none
[download]