This module provides a general-purpose clone function to make deep
copies of Perl data structures. It calls itself recursively to copy
nested hash, array, scalar and reference types, including tied
variables and objects.

The clone() function takes a scalar argument to copy. To duplicate
arrays or hashes, pass them in by reference:

The clone() function also accepts an optional second parameter that
can be used to limit the depth of the copy. If you pass a limit of
0, clone will return the same value you supplied; for a limit of
1, a shallow copy is constructed; for a limit of 2, two layers of
copying are done, and so on.