I am trying to workaround what appears to be TK bug related to browseentry widgets.
What's happening is that when I populate with a long list of choices, then repopulate with a short list of choices, then go back to a long list of choices the scrollbar isn't updating and it appears that I can't scroll.
However I can scroll if select one of the options with mouse1 down and drag down then the scroll slider widget reappears.
Also if reselect the drop down arrow then press the long list button again then it is corrected and scroll widget reappears.
I am trying to figure out how to update the widget so the scrollbar appears without having to destroy and recreate the widget or simulate an event to trigger the correct behavior.
I am using the following example: 
#!/usr/bin/perl
use strict;
use Tk;
use Tk::BrowseEntry;
my $mw = MainWindow->new;

# Mainwindow: sizex/y, positionx/y
$mw->geometry("200x200+100+120");
my $shortlist = [qw(a b c d)];
my $longlist = [qw(a b c d e f g h i j k l m n o p r s t u w)];
&create_dropdown($mw);
MainLoop;

sub create_dropdown {
    my $mother  = shift;
    # Create dropdown and another element which shows my selection
    my $dropdown_value;
    my $dropdown = $mother->BrowseEntry(
        -label => "Label",
        -variable => \$dropdown_value,
        -autolimitheight => 1
        )->pack;

    $mother->Button( -text => "Short List", -command => sub{ 
        $dropdown->configure(-choices => $shortlist)})->pack;
    $mother->Button( -text => "Long List", -command => sub{ 
        $dropdown->configure(-choices => $longlist)})->pack;

    # Populate dropdown with values
    $dropdown->configure(-choices => $longlist, -autolimitheight => 1)
+;
    return;

}

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In reply to BrowseEntry scrollbar not updating by smaclach

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