Encapsulation of an object means you should never access attributes directly but use accessors and mutators(getters and setters).

This is only partially true. Encapsulation means that you have private data which is not accessible from the "outside" (or more specifically, you can control the accessibility). What you are doing with AUTOLOAD is no better then just accessing the underlying hash directly.

IMO accessors and mutators should only be created when a truly valid need exists for them. Objects are meant to be a collection of (encapsulated) data and behaviors, but if all your behaviors are simply accessors/mutators, then you might as well just have a struct/record-type.