Functions for accessing a hash's internal iterator
Description
In perl all hashes have an internal iterator. This iterator is used by the
each() function, as well as by keys() and values(). Because these all share use
of the same iterator, they tend to interact badly with each other when nested.
Hash::StoredIterator gives you access to get, set, and init the iterator inside
a hash. This allows you to store the current iterator, use each / keys / values
etc., and then restore the iterator, which helps you to ensure you do not
interact badly with other users of the iterator.
Along with low-level get / set / init functions, there are also 2 variations of
each() that let you act upon each key/value pair in a safer way than vanilla
each().
This module can also export new implementations of keys() and values() that
stash and restore the iterator so that they are safe to use within each().
