my @mac_addrs = ("0015FAA3F03A", "0015FAA3F03B", "0015FAA3F03C");

sub convert {
    return map { "AP" . join ".", unpack "(A4)*", lc $_ } @_;
}

print "$_\n" for convert(@mac_addrs);

##</code><code>##

$ perl -le '@a = (2, 3, 4, 5); @b = map { 2 * $_ } @a; print for @b'
4
6
8
10

##</code><code>##

$ perl -le '@a = (2, 3, 4, 5); @b = map { $_ % 2 ? () : ($_, $_ / 2) } @a; print for @b'
2
1
4
2

##</code><code>##

$ perl -le '@mac_addrs = ("0015FAA3F03A", "0015FAA3F03B", "0015FAA3F03C"); @a = map { lc $_ } @mac_addrs; print for @a'
0015faa3f03a
0015faa3f03b
0015faa3f03c

##</code><code>##

$ perl -le '@mac_addrs = ("0015FAA3F03A", "0015FAA3F03B", "0015FAA3F03C"); @a = map { unpack "(A4)*", lc $_ } @mac_addrs; print for @a'
0015
faa3
f03a
0015
faa3
f03b
0015
faa3
f03c

##</code><code>##

$ perl -le '@mac_addrs = ("0015FAA3F03A", "0015FAA3F03B", "0015FAA3F03C"); @a = map { join ".", unpack "(A4)*", lc $_ } @mac_addrs; print for @a'
0015.faa3.f03a
0015.faa3.f03b
0015.faa3.f03c

##</code><code>##

@mac_addrs = ("0015FAA3F03A", "0015FAA3F03B", "0015FAA3F03C"); @a = map { "AP" . join ".", unpack "(A4)*", lc $_ } @mac_addrs; print for @a'
AP0015.faa3.f03a
AP0015.faa3.f03b
AP0015.faa3.f03c

##</code><code>##

$ perl -le '
> use strict;
> my @mac_addrs = ("0015FAA3F03A", "0015FAA3F03B", "0015FAA3F03C");
> sub convert {
>   map { "AP" . join ".", unpack "(A4)*", lc $_ } @_
> }
> print for convert @mac_addrs
> '
AP0015.faa3.f03a
AP0015.faa3.f03b
AP0015.faa3.f03c