I can't seem to get the openoffice ebulid to build with wordperfect support. I grepped the ebuild for libwpd and it doesn't seem to be in there, so I assume support has not yet been concidered. According to the following link it would work: http://www.oooauthors.org/FAQs/faqcompatibility/faqgeneralcompatibilityoffice/20040921a
This functionality is not yet included in OOo 1.1.x, it will come with the 2.0-series. At the moment if you really need this use openoffice-ximian