I've looked. Heap::Fibonacci is one of the three engines of the Heap module.

Heap::Simple::XS in an engine for Heap::Simple, although it's distributed separately (I guess that's to keep Heap::Simple a pure-perl module). The other engine is Heap::Simple::Perl.

Both of Heap and Heap::Simple are written in such a way that they can have more than one backend.

If you really want to know, the other heap modules on CPAN are not these but Array::Heap2 and Heap::Priority. I've glanced at those too at that time, but I don't remember my conclusion about them.