'Data::Clone' does data cloning, i.e. copies things recursively. This is
smart so that it works with not only non-blessed references, but also with
blessed references (i.e. objects). When 'clone()' finds an object, it calls
a 'clone' method of the object if the object has a 'clone', otherwise it
makes a surface copy of the object. That is, this module does polymorphic
data cloning.

Although there are several modules on CPAN which can clone data, this
module has a different cloning policy from almost all of them. See the
/Cloning policy manpage and the /Comparison to other cloning modules
manpage for details.

Cloning policy
A cloning policy is a rule that how a cloning routine copies data. Here
is the cloning policy of 'Data::Clone'.