use MIME::Words qw( decode_mimewords );
use Encode      qw( decode );

sub mime_decode {
   my $decoded = '';
   foreach (decode_mimewords($_[0])) {
      my ($data, $charset) = @$_;
      if (defined($charset)) {
         $decoded .= decode($charset, $data);
      } else {
         $decoded .= $data;
      }
   }
   return $decoded;
}

$subj = mime_decode($subj);