package.conf os grouping options

In the Application Packaging Guide there is an example in the "Global" section for how to add os dependent variables.

 sfc_exe \\\$(package)/bin/win32/psurf.exe sfc_ver 2.4.5   sfc_exe \\\$(package)/bin/linux32/psurf sfc_ver 2.4.7 


I would like to know which "os" values are acceptable. Specifically, it seems users on 64 bit linux platforms do not get the variables in the "linux32" section, so I'm wondering if I need to duplicate the section to a "linux64" one or it is possible to use a some "wildcard" to catch all linux variants.

TIA