The second suggestion is violated by the standard distribution (AnyDBM_File, GDBM_File, NDBM_File, SDBM_File), although it could be argued they are just .pm files, and don't use class names with '::' in them. But a quick scan of the file sources/modules/02packages.details.txt.gz shows several name spaces that use an underscore in the first component. (CDB_File, DB_File, DWH_File, heavy_template).

I think that in theory the way Perl and CPAN works is that it is very hard to make sure there are no name clashes. I think that practise has shown that there's not much of a problem.

Abigail