open my $fh, ">:raw:encoding(UTF-16LE):crlf:utf8", "ok.utf16" or die;
print $fh "h\x{00e4}llo\n";

$ od -tx1 -An ok.utf16
 68 00 e4 00 6c 00 6c 00 6f 00 0d 00 0a 00