fixed DHCPv6 testing format error

perftest.pl

 #!/usr/bin/perl
-#   Copyright 2019 Pascal Gloor
-#
-#   Licensed under the Apache License, Version 2.0 (the "License");
-#   you may not use this file except in compliance with the License.
-#   You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-#   Unless required by applicable law or agreed to in writing, software
-#   distributed under the License is distributed on an "AS IS" BASIS,
-#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-#   See the License for the specific language governing permissions and
-#   limitations under the License.
-
 
 use strict;
 use IO::Socket::INET;
 
 		$hdr .= pack("H2", "01"); # msg-type
 		$hdr .= pack("H6", "000000"); # transaction-id
-		$hdr .= pack("C", 1); # DUID option
-		$hdr .= pack("C", 6); # DUID length
+		$hdr .= pack("n", 1); # DUID option
+		$hdr .= pack("n", 6); # DUID length
 	}
 	else { # IPv4
 		$sock = IO::Socket::INET->new(