As I read the doc, there is one 'overall' default timeout value (that is set to 10 seconds) which you can get/set via the timeout() method like

 $secs = $telnet->timeout;

 $prev = $telnet->timeout($secs);
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Also, you might finetune your way of operation by changing the timeout for a specific command, like

$ok = $obj->cmd( String  => "xxx",
                 Timeout => $secs,
      );
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