Here is some test code I am using to try and resolve the problem

#!/usr/bin/perl

use Encode;
use Encode::CN;
use Encode::TW;
use MIME::EncWords qw ( /decode_mimewords/);

binmode STDOUT, ":utf8";

my $text = "=?gb2312?B?RFBNMjAwN2V4Y2hhbmdl64rgXcVj4F3P5NDej80uemlw?="
+;

my(@chunks) = decode_mimewords($text);
for my $pair (@chunks) {
   my($data,$encoding) = @$pair;
   my $filename = Encode::decode($encoding,$data);
   print $filename . "\n";
}
[download]