# as UNC (beware the proper rights)
my $DSN = 'driver=Microsoft Access Driver(*.mdb);dbq=\\\\cheese\\g$\\perltest.mdb'; 
# or just as plain filename:
my $DSN = 'driver=Microsoft Access Driver(*.mdb);dbq=g:\\perltest.mdb';

my $dbh = DBI->connect("dbi:ODBC:$DSN", '','') or
  die "$DBI::errstr\n";