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.