&_fillbuf($self, $s, 0);

##</code><code>##

require Net::Telnet;
{
no warnings 'redefine';
*Net::Telnet::_fillbuf = sub {
    ...
};
};

my $connectObj = Net::Telnet->new();
$connectObj->open(
    Host        => 'iberiamud.mooo.com',
    Port        => 5900,
);