Also you may try to replace can_read calls used to timeout connections in NET::DNS::Nameserver to something like this:

eval {
local $SIG{ALRM} = sub { die “Timed Out” };
alarm 1;
### IO function call goes here
alarm 0;
};
if ($@ and $@ !~ /Timed Out/) {
die
}

This should give a 1 second timeout on the function call.

PS: You may aslo try to look through this article:
http://www.perlmonks.org/index.pl?node_id=193076