use 5.010;  # needs  \K  \g-1

use warnings;
use strict;

use Test::More 'no_plan';
use Test::NoWarnings;

VECTOR:
for my $ar_vector (
    "ALL of these shall be converted",
    [ '28:8a:1c:59:cc:85' => '288a.1c59.cc85' ],
    [ '28-8a-1c-59-cc-85' => '288a.1c59.cc85' ],

    "NONE of these shall be converted",
    map [ ($_) x 2 ],  # string unchanged, so input expected as output
    # inconsistent separator usage
    qw(28:8a-1c-59-cc-85
       28-8a-1c-59-cc:85
       28-8a:1c:59:cc:85
       28:8a:1c:59:cc-85
       28:8a:1c-59:cc:85
       28-8a-1c:59-cc-85
       ),
    # too few/too many/malformed octets
    qw(28:8a:1c:59:cc:8
       28:8a:1c:59:cc:
       28-8a-1c-59-cc

       28-8a-1c-59-cc-85-
       28-8a-1c-59-cc-85-8
       28:8a:1c:59:cc:85:88
       28:8a:1c:59:cc:85:888

         -8a-1c-59-cc-85
        8-8a-1c-59-cc-85
      228-8a-1c-59-cc-85
      -28-8a-1c-59-cc-85

       28:8a:1g:59:cc:85:88
       28:8a:1:59:cc:85:88
       28:8a:111:59:cc:85:88
       ),

    ) {

    if (not ref $ar_vector) {
        note $ar_vector;
        next VECTOR;
        }

    my ($mac, $expected) = @$ar_vector;

    my $xx  = qr{ [[:xdigit:]]{2} }xms;
    my $sep = qr{ [-:]            }xms;

    my $converted = (my $final = $mac) =~ s{
          \A         $xx \K ($sep) (?= (?: $xx \g-1){4} $xx \z)
          |
          \G (?! \A) $xx \K  $sep
        }
        {@{[ '', '.' ]}[ $-[0] % 2 ]}xmsg;

    $converted = $converted ? 'converted' : 'NO conversion';

    is $final, $expected, qq{'$mac' -> '$final' ($converted)};

    }  # end for VECTOR

done_testing;

##</code><code>##

c:\@Work\Perl\monks\Anonymous Monk\1159176>perl convert_mac_addr_2.pl
# ALL of these shall be converted
ok 1 - '28:8a:1c:59:cc:85' -> '288a.1c59.cc85' (converted)
ok 2 - '28-8a-1c-59-cc-85' -> '288a.1c59.cc85' (converted)
# NONE of these shall be converted
ok 3 - '28:8a-1c-59-cc-85' -> '28:8a-1c-59-cc-85' (NO conversion)
ok 4 - '28-8a-1c-59-cc:85' -> '28-8a-1c-59-cc:85' (NO conversion)
ok 5 - '28-8a:1c:59:cc:85' -> '28-8a:1c:59:cc:85' (NO conversion)
ok 6 - '28:8a:1c:59:cc-85' -> '28:8a:1c:59:cc-85' (NO conversion)
ok 7 - '28:8a:1c-59:cc:85' -> '28:8a:1c-59:cc:85' (NO conversion)
ok 8 - '28-8a-1c:59-cc-85' -> '28-8a-1c:59-cc-85' (NO conversion)
ok 9 - '28:8a:1c:59:cc:8' -> '28:8a:1c:59:cc:8' (NO conversion)
ok 10 - '28:8a:1c:59:cc:' -> '28:8a:1c:59:cc:' (NO conversion)
ok 11 - '28-8a-1c-59-cc' -> '28-8a-1c-59-cc' (NO conversion)
ok 12 - '28-8a-1c-59-cc-85-' -> '28-8a-1c-59-cc-85-' (NO conversion)
ok 13 - '28-8a-1c-59-cc-85-8' -> '28-8a-1c-59-cc-85-8' (NO conversion)
ok 14 - '28:8a:1c:59:cc:85:88' -> '28:8a:1c:59:cc:85:88' (NO conversion)
ok 15 - '28:8a:1c:59:cc:85:888' -> '28:8a:1c:59:cc:85:888' (NO conversion)
ok 16 - '-8a-1c-59-cc-85' -> '-8a-1c-59-cc-85' (NO conversion)
ok 17 - '8-8a-1c-59-cc-85' -> '8-8a-1c-59-cc-85' (NO conversion)
ok 18 - '228-8a-1c-59-cc-85' -> '228-8a-1c-59-cc-85' (NO conversion)
ok 19 - '-28-8a-1c-59-cc-85' -> '-28-8a-1c-59-cc-85' (NO conversion)
ok 20 - '28:8a:1g:59:cc:85:88' -> '28:8a:1g:59:cc:85:88' (NO conversion)
ok 21 - '28:8a:1:59:cc:85:88' -> '28:8a:1:59:cc:85:88' (NO conversion)
ok 22 - '28:8a:111:59:cc:85:88' -> '28:8a:111:59:cc:85:88' (NO conversion)
1..22
ok 23 - no warnings
1..23