$ perl -MEncode -e'print encode("UTF-8", chr(0xFEFF))' | od -t x1
0000000 ef bb bf
0000003

$ perl -MEncode -e'print encode("UTF-16be", chr(0xFEFF))' | od -t x1
0000000 fe ff
0000002

$ perl -MEncode -e'print encode("UTF-16le", chr(0xFEFF))' | od -t x1
0000000 ff fe
0000002