I've logged a bug for this at https://rt.cpan.org/Public/Bug/Display.html?id=111370 with this info. Hopefully somebody can come up with a fix or a workaround. I'm having to write some ugly code to get around this in the meantime.

As I said above "someone smarter than me" - thanks for coming to the rescue Corion!

I just found and tried this code, still no luck. It still takes 20 to 30 seconds to regain control. From Chapter 18. The UDP Protocol, in "Network Programming with Perl".

eval {
    local $SIG{ALRM} = sub { die "timeout\n" };
    alarm(2);
    $t = new Net::Telnet (Host       => $host,
                          Port       => $port,
                          Timeout    => 1,
                          Prompt     => '/Escape character is.+\n/',
                          Rs         => ' ',
                          Ors        => '',
                          Binmode    => 1,
                          Telnetmode => 1,
                          Errmode    => 'return');
    alarm(0);
};
if ($@) {
    die $@ unless $@ eq "timeout\n";
    warn "Timed out!\n";
}
[download]

I also tried ualarm() from Time::HiRes;

For that it's even worse. I get "Time::HiRes::ualarm(): unimplemented in this platform"

*sigh*