Thx TGI for this very usefull comment.
I gave it a try, but I still encounter some problems:
- every sublist starts with some separator alike dashes. The number of dashes depends of the number of elements in that sublist
- if I add a 'subelement' to an optionmenu later on, then I cannot check if the 'mainpart' of this element already exist
my code:

#!/usr/local/bin/perl
use Tk;
# Main Window
$mw = new MainWindow;

my $var;
my $opt = $mw -> Optionmenu(-options => [qw(opt1 opt2 opt3 opt4 dinner
+1 dinner2 dinner3 dinner4 desert1 desert2 desert3 desert4 desert5 )],
        -variable => \$var )->pack;
$opt->addOptions('dinner5');
$mw->Button(-text=>'Exit', -command=>sub{$mw->destroy})->pack;

MainLoop;
[download]

my changed sub addOptions:

sub addOptions
{
 my $w     = shift;
 my $menu  = $w->menu;
 my $tvar  = $w->cget(-textvariable);
 my $vvar  = $w->cget(-variable);
 my $oldt  = $$tvar;
 my $width = $w->cget('-width');
 my %hash;
 my %MainFields;
 my $first;
 while (@_) {
    my $val = shift;
    my $label = $val;
    if (ref $val) {
        if ($vvar == $tvar) {
            my $new = $label;
            $w->configure(-textvariable => ($tvar = \$new));
        }
        ($label, $val) = @$val;
    }
    my $len = length($label);
    $width = $len if (!defined($width) || $len > $width);

##### BEGIN CHANGED #######
    if ( $label eq '-') { $menu->separator() }
    elsif ( $label =~ /^(\w+)(\d+)$/ ) {
        my ($One, $Two)=($1, $2);
        if ( !defined($MainFields{'DaTa'.$One}) ) {
            $MainFields{'DaTa'.$One}=$menu->Cascade(-label=>$One);
        }
        $MainFields{'DaTa'.$One}->command(-label =>$One.$Two,-command 
+=> [ $w , 'setOption', $One.$Two ]);
    }
    else {
        $menu->command(-label => $label, -command => [ $w , 'setOption
+', $label, $val ]);
    }
##### END CHANGED #######
#    $menu->command(-label => $label, -command => [ $w , 'setOption', 
+$label, $val ]);
    $hash{$label} = $val;
    $first = $label unless defined $first;
}
if (!defined($oldt) || !exists($hash{$oldt})) {
    $w->setOption($first, $hash{$first}) if defined $first;
}
$w->configure('-width' => $width);
}
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.