Here's an answer that allows the use of spaces instead of dashes, or no spacing at all.

( $areacode, $exchange, $line ) = $phn =~ 
    m/(1[-| ]?)?\(?(\d{3})\)?[-| ]?(\d{3})[-| ]?(\d{4})/;
[download]

212-555-1212
(212)555-1213
1-(212)-555-1214
1-212-555-1215
212 555 1216
(212) 555 1217
1 (212) 555 1218
1 212 555 1219
12125551210
[download]

Actually, your regex, while good, has a slight problem. In a character class (something like [a-zA-Z]), the target text is filtered against each individual character in the class. No bar '|' for alternation is necessary. Your class actually is testing for a dash, a bar, and a space, rather than alternating between dash and space. Here's this code slightly cleaned up:

#!/usr/local/bin/perl -w

use strict;

while (<DATA>) {
    s /[\n\r]//g;

    print "Testing with $_, result is ";

    m/(?:1[- ]?)?    # Testing for an leading 1 and dash or space behi
+nd it
        \(?          # Optional parentheses around the area code
          (\d{3})    # Area code
        \)?          # Close optional parentheses around area code
        [- ]?        # Optional dash or space after area code
        (\d{3})      # Exchange
        [- ]?        # Optional dash or space after exchange
        (\d{4})      # Line
    /x;              # /x modifier allows whitespace in a regex

    my $areacode = $1;
    my $exchange = $2;
    my $line     = $3;

    print "($areacode) $exchange-$line\n";
}

__DATA__
212-555-1212
(212)555-1213
1-(212)-555-1214
1-212-555-1215
212 555 1216
(212) 555 1217
1 (212) 555 1218
1 212 555 1219
12125551210
[download]

A couple of notes on the code: when single character alternates are allowed (that's not quite the same thing as single byte alternates), a character class is much faster than alternation. In other words, we're using [- ] rather than (-| ).

I also switched the first set of parentheses from (1[- ]?) to (?:1[- ]?). The (?:someregex) construct allows for grouping without backreferencing to a $somenumber variable. This is more efficient than straight parentheses for grouping and should be used, when possible.

Folks interested in this question might find my thorough (but empirical) treatment of this topic interesting:
Beast of the Number: Parsing the Feral Phone

( undef, $areacode, $exchange, $line ) = $phn =~ 
    m|(1-)?\(?(\d{3})\)?-?(\d{3})-(\d{4})|;
[download]

Here's a regex-less solution:

sub parse_phonenumber
{
    local $_ = shift;
    tr/()\- //d; # eliminate punctuation
    my( $are, $three, $four );
    my $line = substr $_, -4, 4, '';
    my $exch = substr $_, -3, 3, '';
    my $area = substr $_, -3, 3, '';
    ( $area, $exch, $line )
}
[download]

The only CPAN module that comes close to addressing the problem in a comprehensive way is the Number::Phone family of classes. They do a lot more than mere parsing; you may be particularly interested in their format method.

Based on jlistf's answer:

( undef, $areacode, $exchange, $line ) = $phn =~
    m|(1-)?\(?(\d{3})\)?-?(\d{3})-(\d{4})|;
[download]

212-555-1212
(212)555-1213 
1-(212)-555-1214
1-212-555-1215
[download]

Originally posted as a Categorized Answer.

sub fphone {
    shift;
    s/[\s|\n|\r]//g;    # strip space and newlines
    s/[-|)|(|.]//g;     # strip seperating chars
    s/(x|ex|ext\.)(.*)$//;      # Extension
    my $ext = $2;       # save extension
    my $n = '';
    my $l = length($_);
    if (($l == 12)||($l == 13)) {
        m/(\+\d{2}|\d{3})(\d{3})(\d{3})(\d{3})/;
        $n .= "$1 $2 $3 $4";
    } elsif (length == 11) {                # us with leading 1
        s/[+]//g;
        m/(\D)?(\d{3})(\d{3})(\d{4})/;
        $n .= "$1 " if $1 =~ /\d/;
        $n .= "($2) $3-$4";
    } elsif ($l == 10) {                    # us regular
        s/[+]//g;
        m/(\d{3})(\d{3})(\d{4})/;
        $n .= "($1) $2-$3";
    } else {
        s/(\d\d\d)/$1 /g;
        $n .= $_;
    }
    $n .= " Ext. $ext" if $ext;
    return $n;
}
[download]

I might have tried to generalize that even further, though you still have regional issues to worry about. I.e. this won't work for everyone:

@FORMAT_PHONE = (
   '%d%d%d',                              # 911 
   '%d-%d%d%d',                           # 1-411
   '%d-%d%d%d%d',                         # 5-1212 ?
   '%d%d-%d%d%d%d',                       # 55-1212 ?
   '%d%d%d-%d%d%d%d',                     # 555-1212
   '%d-%d%d%d-%d%d%d%d',                  # 1-222-2345
   '%d%d%d-%d%d%d-%d%d%d',                # 212-114-151 ?
   '(%d%d%d) %d%d%d-%d%d%d%d',            # (800) 555-1212
   '+%d (%d%d%d) %d%d%d-%d%d%d%d',        # +1 (800) 555-1212
   '+%d%d (%d%d%d) %d%d%d-%d%d%d%d',      # +01 (800) 555-1212
   '+%d%d%d (%d%d%d) %d%d%d-%d%d%d%d',    # +011 (800) 555-1212
   '+%d%d%d %d (%d%d%d) %d%d%d-%d%d%d%d', # +011 1 (800) 555-1212
   '%d%d%d%d%d (%d%d%d) %d%d%d-%d%d%d%d', # 10321 (800) 555-1212
   '%d%d%d%d%d %d (%d%d%d) %d%d%d-%d%d%d%d',  # 10321 1 (800) 555-1212
   '%d%d%d%d-%d%d%d (%d%d%d) %d%d%d-%d%d%d%d', # 1010-220 (800) 555-12
+12
   '%d%d%d%d-%d%d%d %d (%d%d%d) %d%d%d-%d%d%d%d', # 1010-220 1 (800) 5
+55-1212
   # etc...
);

my %L2M;
@L2M{qw: Q Z   :} = 1;
@L2M{qw: A B C :} = 2;
@L2M{qw: D E F :} = 3;
@L2M{qw: G H I :} = 4;
@L2M{qw: J K L :} = 5;
@L2M{qw: M N O :} = 6;
@L2M{qw: P R S :} = 7;   # some define this as PQRS
@L2M{qw: T U V :} = 8;
@L2M{qw: W X Y :} = 9;   # some define this as WXYZ
   
sub format_phone {
   my $number = shift;
   $number =~ s/[a-zA-Z]/$L2M{uc($1)}/eg;
   $number =~ s/\D//g;       # maybe allow # and * later??

   if (defined($FORMAT_PHONE[length($number)-3])) {
      return sprintf($FORMAT_PHONE[length($number)-3], split(//, $numb
+er));
   }

   return;
}
[download]

Originally posted as a Categorized Answer.