Hash::fieldhash provides the field hash mechanism which supports the inside-out technique.

you may know hash::util::fieldhash. it's a very useful module, but too complex to understand all the functions.

this is an alternative to hash::util::fieldhash with following features:

simpler interface

hash::fieldhash provides a few functions: fieldhash() and fieldhashes().
that's enough.
higher performance
hash::fieldhash is faster than hash::util::fieldhash, because its internals
use simpler structures.