sub test_regex {
    local $_ = shift;
    local $\ = "\n";

    print 'string:     ', $_, ;
    print 'with \G:    ', join(':', m/\G ( [0-9A-Z]{1,2} ) (?: :|$ ) /igx);
    print 'without \G: ', join(':', m/   ( [0-9A-Z]{1,2} ) (?: :|$ ) /igx), "\n";
}

test_regex('0:0A:0C:B:B8:F');
test_regex('#0:0A:0C:B:B8:F');
test_regex('0: 0A:0C:B:B8:F');
test_regex('0:0Aa:0C:B:B8:F');