A file with the extension mdf is a binary file format produced by Microsoft Access. There are several ways in the Perl world to programatically open, read, and manipulate such a file:

• If you are on a Windows machine with Microsoft Access installed, you can use Win32::OLE to open Access and get data from the file. There is some information in Ms Access and win32 ole, but it seems that unlike Excel, there is not as much information on manipulating Access using OLE via Perl.
• You can, again on Windows, create an ODBC DSN that can be used in conjunction with DBI and DBD::ODBC to treat Access as just another database server.
• You can, instead of ODBC, read using an ADO connection to Access. This, again, is a Microsoft Windows solution.
• If you're not on Windows (hopefully using a nice Perl stack like Strawberry Perl or ActiveState's Perl), then you might be able to get away with using MDB Tools and convert your mdb file into some other format.