$ perl
use warnings;
use strict;
use Encode qw/decode/;
use Data::Dumper qw/Dumper/;


warn Dumper decode('UTF-16-BE', "\x3D\xDD\xFA", Encode::FB_CROAK|Encode::LEAVE_SRC );
warn Dumper decode('UTF-16-BE', "\xFA",         Encode::FB_CROAK|Encode::LEAVE_SRC );

warn Dumper decode('UTF-16-LE', "\xD8\xFA\xDD", Encode::FB_CROAK|Encode::LEAVE_SRC );
warn Dumper decode('UTF-16-LE', "\xDD",         Encode::FB_CROAK|Encode::LEAVE_SRC);

__END__
$VAR1 = "\x{3ddd}";
$VAR1 = '';
$VAR1 = "\x{fad8}";
$VAR1 = '';

 MINGW64 ~
$ perl -v

This is perl 5, version 26, subversion 2 (v5.26.2) built for x86_64-msys-thread-multi