use strict;
use warnings;
use Net::Telnet;

my $telnet = new Net::Telnet (Timeout => 10, Errmode=>'return', Port=>1810, Prompt => '/[\$%#>] $/' );
my $fh = $telnet->dump_log( 'test.log' );

$telnet->open('PC110197');
$telnet->errmode( sub{ return @_ unless $_[0] =~ /eof/ } );

$telnet->cmd('CLIENT CREATE');
my $data = $telnet->buffer;
my ($message) = split /\0/, $$data;

if ($message eq "ACK")
{
  print "CLIENT CREATE BESTAETIGT!!!";
  $telnet->cmd('CONNECT');
  $telnet->buffer_empty;
  my $data2 = $telnet->buffer;
  my ($message2) = split /\0/, $$data2;

  if ($message2 eq "ACK")
  {
    print "CONNECT BESTAETIGT!!!";
  }
  else
  {
    print "CONNECT NICHT BESTAETIGT!!!";
  }

}
else
{
  print "CLIENT CREATE NICHT BESTAETIGT!!!";
}

Use of uninitialized value in string eq at prog4.pl line 23.
CLIENT CREATE BESTAETIGT!!!CONNECT NICHT BESTAETIGT!!!