# MainWindow  $MW
# Frame         Frame1
# Labelframe      SourceFrame
# Label             SourceTypeLabel
# Optionmenu        SourceTypeMenu
# Frame             sourceoneFrame # Mutually exclusive
# Frame             sourcetwoFrame # Mutually exclusive
# Label             StringLabel

##</code><code>##

  -command  =>
    $typeframes{'source'}->{ $config{'sourcetype'} }->( \%tkobjects ),

##</code><code>##

    # $option_command will be an anon sub,
    # with sole access to %typeframes.
    my $option_command;
    {
      my %typeframes = (
          'source' => {
              'one' => \&makeSourceoneFrame,
              'two' => \&makeSourcetwoFrame,
          }
      );
      $option_command = sub {
        my $option = shift;
        $typeframes{'source'}->{ $option }->( \%tkobjects );
      }
    }

    $tkobjects{'SourceTypeMenu'}
      = $tkobjects{SourceFrame}->Optionmenu(
#        -variable => \$config{'sourcetype'}, # No longer needed!
        -command  => $option_command,
        -options => \@TYPES
      )->grid(
        -row    => 1,
        -column => 1,
      );

    # By naming the anon sub (via variable), we avoid
    # repeating code here.
    $option_command->('one');
    # Actually, we don't have to manually invoke $option_command;
    # it got called with the first (default) option when
    # the OptionMenu was created!

    MainLoop;