A long property name is certainly going to discourage people from using them directly (we are perl programmers after all ;-), but there are other options.
in reply to A new take on affordance.
For example if you're just creating read-only accessors then you could use the closure method for creating RO accessors as described in Tom Christiansen's perltoot.
There's also Michael Schwern's Class::Accessor which will perform all the accessor creating magic for you.
As people have previously discussed, OO in perl is like asking people not to come into your house as opposed to standing at the front door with a shotgun and a twitch in your right eye. So you may want to fall on the B&D side of property accessors or take the perl approach and ask people kindly not to mess with the object properties as it could do any() or all() of x,y, and z.