In your set_request, you are attempting to set multiple values.

Looking at the code (PDU module), this is how it analyzes the trios:

 #-- the "-varbindlist' array ref is assigned to $trios
   my $pairs = [];
   for (my $i = 0; $i < $#{$trios}; $i += 3) {
      if ($trios->[$i] !~ /^\.?\d+\.\d+(?:\.\d+)*/) {
         return $this->_error('Expected OBJECT IDENTIFIER in dotted no
+tation');
      }
      push(@{$pairs},
         OBJECT_IDENTIFIER, $trios->[$i], $trios->[$i+1], $trios->[$i+
+2]
      );
   }
[download]

Analyzing this, what it appears to be expecting is a SINGLE array ref containing triplets .. perhaps something like (untested):

    -varbindlist =>[
                                   $TransferServerOID,OCTET_STRING,$Tr
+ansferServer,
                                   $TransferLoginNameOID,OCTET_STRING,
+$TransferLogin,
                                   $TransferPasswordOID,OCTET_STRING,$
+TransferPass,
                                   $TransferCommandOID,'HmsSysCommandT
+ype',$TransferCommand,
                                   $TransferManifestOID,OCTET_STRING,$
+wamfile
                                   ]);
[download]

UpdateAak! - ignore this nonsense - code scan malfunction - Your code is equivalent to my suggestion.