You need to change the value of Errmode when you initialize the Net::Telnet object.

Errmode=>'die' tells the program to abort if there is an error (and failing to connect to a host is an error). I would suggest you do the following:

$telnet = new Net::Telnet ( Timeout=>10, Errmode=>'return');
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which will return undef if there is a connect failure. You can then test the return value of $telnet->open("$hosts$x"); for undef and proceed as you wish. One possibility:

use Net::Telnet; 

@hosts = ("ncc1","ncc2","ncc3");
for ($x=0; $x <= $#hosts; $x++) {
    $telnet = new Net::Telnet ( Timeout=>10, Errmode=>'return'); 
    $result = $telnet->open("$hosts$x"); 
    if($result) {
        $telnet->login('test', 'testuser'); 
        my @arr = $telnet->cmd('ifconfig -a'); 
        $telnet->close("$host"); 
        print "\n Probe - $host \n"; print "\n @arr \n" ;
    } else {
        print $telnet->errmsg . "\n";
    }
}
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I would suggest you read the Net::Telnet manpage

Hope this helps,
davidj