[Puppet Users] Hierachy for facts?

We're working on prototpying facter+puppet for our environment and
wondering what the generally accepted best-pratices are for handling
hierarchical custom facts in facter. Right now, we're using underscores.


For example, if I'm collecting infromation about the raid array, it would
be something like this:
---
custom_hw_localstorage_ctrl_0_array_0_raid => 1
custom_hw_localstorage_ctrl_0_array_1_raid => 5
---

Where the implied hierachy is something like:
custom
hw
localstorage
ctrl
0: array
0: raid = 1
1: raid = 5

And of course, there would be many, many more sub-items under "custom",
"hw", "localstorage", etc...

I'm using the facter 2 and puppet 3 RCs and I know they have hiera
included, but I'm not sure if or how that could help with this. Ultimately,
I'd like to be able to use these facts for decision making in puppet.

Thanks!