KiokuDB::Role::Immutable::Transitive - A role for immutable objects that only point at other such objects.

    with qw(KiokuDB::Role::Immutable::Transitive);

This role makes a stronger promise than KiokuDB::Role::Immutable, namely that this object and all objects it points to are immutable.

These objects can be freely cached as live instances, since none of the data they keep live is ever updated.