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 and only available in 5.10. H::U::F::Compat is available for pre-5.10, but it seems too slow to use. This is an alternative to H::U::F 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. Relic support - Although Hash::FieldHash uses a new feature introduced in Perl 5.10, the uvar magic for hashes described in "GUTS" in Hash::Util::Fieldhash, it supports Perl 5.8 using the traditional tie-hash layer. WWW: http://search.cpan.org/dist/Hash-FieldHash/