In fact, the link you cited talks about a A-VI to CSV/LDIF/COBOL/ISAM/etc conversion tool. You might start with that tool and see how far that gets you. Note: they also point you in the direction of "Acucorp, Inc.'s Complementary Technology Program (CTP)". Becoming a member in the CTP will probably get you access to the formats you desire.

Also take a look at this Document, it talks about using ODBC with A-VI

I suspect that this particular black-box data format has not been reverse-engineered due to the lack of a large body of Users (as opposed to SMB, when Samba was first developed). If you can demonstrate to the owners of A-VI that having an open format for their product would produce a material benefit for them, they might be amenable to allowing you to build the appropriate Perl bindings.

Good Luck, and Good Night.