use Net::Ping; my $addr = get_local_addr("ppp0"); unless(defined $addr) { die "I'm offline\n"; } while (1) { my $p = Net::Ping->new(udp); if $p->ping($host) { print "success\n"; } else { print "failed\n"; my $cur_addr = get_local_addr("ppp0"); if ($addr ne $cur_addr) { die "I'm offline\n"; } } undef $p; sleep 3; }