Granted, according to the docs, my snippet will say $host is alive if it accepts connections on port 80. This might or might not mean that a webserver is running, just that something is listening there

No, that's the problem, it even says $host is alive if nothing is listening there and the connection is refused (because Net::Ping concludes that the host is up to be able to refuse the connection). It only says $host is dead if it gets no reply whatsoever or an icmp unreachable or so.

•Update: oops, I missed the second part before I replied..

Double ah. So the darn thing answers true if it gets a RST as well.

Yes, exactly :-)