how about trying these? just playing with your fastest and adding sentinal ':'s before processing and removing them after. 
   zen3 => 'my $mac = ":".$data.":"; $mac =~ s/(?<=:)(?=[0-9a-fA-F](?:
+:))/0/g;
                                     $mac =~ s/^:|:$//; $mac;',

   zen4 => 'my $mac = ":$data:"; $mac =~ s/(?<=:)(?=[0-9a-fA-F](?::))/
+0/g;
                                 $mac =~ s/^:|:$//; $mac;',

   zen5 => 'my $mac = ":$data:"; $mac =~ s/(?<=:)(?=[0-9a-fA-F](?::))/
+0/g;
                                 $mac = substr $mac, 1,-1; $mac;',

[download]
my results are varied: 
             Rate     zen2     zen3 ike_fast     zen4     zen5
zen2     152990/s       --      -1%      -1%      -4%      -6%
zen3     154915/s       1%       --      -0%      -3%      -5%
ike_fast 155051/s       1%       0%       --      -3%      -5%
zen4     159115/s       4%       3%       3%       --      -2%
zen5     162584/s       6%       5%       5%       2%       --

             Rate     zen2 ike_fast     zen4     zen3     zen5
zen2     147082/s       --      -3%      -3%      -3%      -5%
ike_fast 150866/s       3%       --      -0%      -1%      -3%
zen4     151345/s       3%       0%       --      -1%      -3%
zen3     152312/s       4%       1%       1%       --      -2%
zen5     155404/s       6%       3%       3%       2%       --

             Rate     zen2 ike_fast     zen4     zen5     zen3
zen2     132209/s       --      -1%      -4%     -10%     -13%
ike_fast 134054/s       1%       --      -3%      -9%     -11%
zen4     137554/s       4%       3%       --      -6%      -9%
zen5     147053/s      11%      10%       7%       --      -3%
zen3     151234/s      14%      13%      10%       3%       --

             Rate     zen2 ike_fast     zen3     zen4     zen5
zen2     148516/s       --      -2%      -3%      -4%      -7%
ike_fast 151827/s       2%       --      -1%      -1%      -5%
zen3     153467/s       3%       1%       --      -0%      -4%
zen4     153946/s       4%       1%       0%       --      -4%
zen5     159757/s       8%       5%       4%       4%       --

[download]

In reply to Re^4: Regex overlap in MAC address by Anonymous Monk
in thread Regex overlap in MAC address by superfrink

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