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.

In reply to RE: Answer: How do I break down a phone number and rebuild it? by Ovid
in thread How do I parse a telephone number? by mofo

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.