moritz is right. Since you are a beginner, here is some more help. Make your listboxes as globals, then empty them and refill. Also, you probably don't need to make your scrollbars as separate widgets....thats the hard way. Use the Scrolled widget

 my $box = $mw->Scrolled('Listbox',
 -scrollbars => 'osoe',     #only show bars if needed
 -relief => 'sunken',
 -height  => 5,
 -setgrid => 0,
);
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The only time you need to address the scrollbars as separate widgets, is if you want to position them manually from within the program, or have dual linked scrollbars. But even then, you can get the bar from the subwidget method.

my $xscrollbar = $scrolled_box->Subwidget('xscrollbar');
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