The Object::Realize::Later class helps with implementing transparent on
demand realization of object data.  This is related to the tricks on
autoloading of data, the lesser known cousin of autoloading of
functionality.

On demand realization is all about performance gain.  Why should you
spent costly time on realizing an object, when the data on the object is
never (or not yet) used?  In interactive programs, postponed realization
may boost start-up: the realization of objects is triggered by the use,
so spread over time.

WWW: http://search.cpan.org/dist/Object-Realize-Later/