Thanks for the quick replies! I have found another solution that works exactly as needed.

This is my first time building a "bigger" gui and I had some problems with usage of tcl and tk in the tkx namespace.

What I wanted:
- popup with a message
- scrollbar ( message can be long )
- let script wait until this popup is closed

Here my solution:

my $mw = Tkx::widget->new(".");

#somewhere else a popup sub
sub scrolled_message_box {
    my ( $mw, $message ) = @_;
    my $child   = $self->mw->new___toplevel();
    my $textbox = $child->new_tkx_Scrolled('text');
    
    $textbox->insert_end( $message );

    $textbox->configure(
        -state => "disabled",
        -wrap  => "none",
    );

    $textbox->g_pack( -expand => 1, -fill => 'both' );

    #this is what I was looking for
    #part of the problem was that I did not know 
    #how to access tcl namespace ( Tkx::__tclExpression )
    Tkx::__tkwait('window', '.t');
}
[download]

What does the documentation say?