$FSref = $top->FileSelect(-directory => $start_dir);
               $top            - a window reference, e.g. MainWindow->new
               $start_dir      - the starting point for the FileSelect
 $file = $FSref->Show;
               Executes the fileselector until either a filename is
               accepted or the user hits Cancel. Returns the filename
               or the empty string, respectively, and unmaps the
               FileSelect.
 $FSref->configure(option => value[, ...])
               Please see the Populate subroutine as the configuration
               list changes rapidly.