A quick scan at CPAN doesn't turn up anything for "MYOB". Maybe if you happen to have any sort of documentation or samples of the file format(s) that MYOB uses/supports, that would be a place to start.

It might not be too bad a stretch for someone to build a suitable set of perl modules, if this software isn't too much in the Microsoft design paradigm... (i.e. arcane, proprietary, and fiercy secretive about it).