Package alternatives?

[Steffen Grunewald]

We're in the process of replacing some packages ("A") by specially built 
ones ("B"), which will be named slightly differently, to avoid confusion.
For FAI this means that we want to
"install package B if it already exists, otherwise use A".
How can this be achieved?

Cheers,
 Steffen

-- 
Steffen Grunewald * MPI Grav.Phys.(AEI) * Am Mühlenberg 1, D-14476 Potsdam
Cluster Admin * http://pandora.aei.mpg.de/merlin/ * http://www.aei.mpg.de/
* e-mail: steffen.grunewald(*)aei.mpg.de * +49-331-567-{fon:7274,fax:7298}