No, in my opinion it isn't, the implementation of persistent variables is in charge of the developer but when the reference count reaches zero, launch DESTROY and saves the values, in this case.

It's not necessary to call undef, perhaps you are talking about mod_perl.

lol! yes! i love the lastest thing so i can improve my knowledge, MySql6 has new feature and it's good to learn, i have this server for more than a year and never crash, don't be panic! of course i use it on my pc, never think in production enviroment!

Cheers!