If your application knows where to find the db, it hardly matters to perl. The issue is interesting, though, because the answer varies according to the type of data and the nature of the system where it's installed.

It is a good idea to avoid cluttering the PERL5LIB path with files you will not be seeking. The same goes for PATH, MANPATH, LD_LIBRARY_PATH, etc. Don't uselessly overpopulate search paths.

If the db is read only and may have wider use, one of the /*/share/ hierarchies might be a good choice. If the need may arise to write to the db, /var would be preferred. On a box you don't control, a ~/share or ~/data directory might be the place.

On Linux, 'man 7 hier' describes the logic behind the filesystem organization. The man page is based on the FHS document. FHS was recently revised as part of the Linux Standard Base.

Update: Added link to FHS. Swore to quit anthropomorphising perl.

After Compline,
Zaxo