If someone is taking the time to sniff packets on your network, then you have likely got a lot more to worry about then just your perlmonks password.
the time is just a simple dsniff that runs in the background.

Also you should consider what kind of network you are on. Say you are at work, well then its likely you're on a switched network
switched networks are no real match, as you can fake packets that will confuse the switch, so you can get all the packages you want. I think especially as a security expert you shouldn't feel all safe because its may seem hard it do - as long as it is possible there is the danger.

By the way, hackers are not people who enter into machines and try to harm others.
see here