If I understand your question like this: How can I read a received MMS from my mobile device' storage? then I suggest to have a look at OBEX and OBEXFTP.

With another obexFTP tool, I managed to browse through the directory system of my mobiles SIM- and memory-card via USB and was able to up-/download files. So the approach should work in principle, although I've never done that using Perl. Since your mobile might have its own directory structure, exploring it with obexftp (they claim to have a Perl language binding) could be a first step.

Here is the openobex Wiki. Good luck.

Update: Perl Client Example