Before you put a class into the @ISA, you should have loaded that base class by using it. The base pragma does both steps for you though:

  package SDU::CommandHandlerSDU;
  use base 'SDU::CommandHandler';
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My guess is, that you are not using the base pragma and you are also not loading the package SDU::CommandHandler into your namespace, but it is hard to tell, as you didn't post your script ./tobj.pl for inspection either.

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web
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