$ 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