I recently finished installing DBD::Oracle at work (on Linux but it should be the same for MS) and my observation is that you do need a client installed for the final result to work.
For this particular case I compiled DBD::Oracle as an rpm on one box for installation on another box (target box has no compilers). I was able to compile against the 10g Instant client so there was no need to do a full blown oracle-installer umpteen MB client install. In the end, installing it on the target box was as easy as installing the (required) instant client and DBD::Oracle rpms.
IIRC the 10g client should work fine for connecting to an 8.1.7 database.