I'm not an expert in DBD::Oracle things, but I think there are essentially two approaches. Either build/install the lib (and don't forget to add its location to LD_LIBRARY_PATH), or figure out what exactly is requiring that lib (ldd -s Oracle.so should tell you), and then see whether it is possible to rebuild / relink / reconfigure /... that other lib in an alternative way, such that it no longer depends on libmm. (Not sure why your other installation isn't depending on it -- maybe it's been linked in statically...).   Good luck.