I totally agree with Sifmole here, in this case you should really use a DB, which can be as simple as File::Gdbm, which uses key => value indexed files, or DBD::SQLite, a lightweight DBMS which comes with the module.

I think it's time to start working on my next lightning talk, entitled "Stop using XML everywhere Damnit!".

And yes, your tag names are really suspect, if you want to stick to XML::Simple have a look at the keyattr option an use elements that look like <visitor ip="127.0.0.1" ... />