[Haskell] Using hs-plugins

[Thomas Davie]

I've been trying to get hs-plugins working on a box, to use the Eval  
module, but the register script seems not to register the eval  
package, or the printf module, which judging by the readme:

---
And to unregister (maybe as root). Note that the unistall order
matters:

         $ ghc-pkg -r printf
         $ ghc-pkg -r eval
         $ ghc-pkg -r plugins
         $ ghc-pkg -r hi
         $ ghc-pkg -r altdata
---

it should have registered.  Have I missed something really obvious?

Bob