Hash::Ordered implements an ordered hash, meaning that it associates keys with
values like a Perl hash, but keeps the keys in a consistent order. Because it is
implemented as an object and manipulated with method calls, it is much slower
than a Perl hash. This is the cost of keeping order.

However, compared to other ordered hash implementations, Hash::Ordered is
optimized for getting and setting individual elements and is generally faster at
most other tasks as well. For specific details, see Hash::Ordered::Benchmarks.