$ 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