it means that either $SERVER{$key}{one} or $SERVER{$key}{two} is undef.

As for what the correct way to solve it is, that depends on the application itself. If it's critical that these variables do have some meaning, something like die "server key one not defined" unless defined ($SERVER{$key}{one}); will tell you when the first one's undefined. If it's ok, then there's a variety of things you can do, but you'll need to check for definedness in (I think) any case.