Hi jinnicky,

Another alternative which seems to work is to change -variable to -textvar:

#!/usr/bin/perl -w

use strict;
use warnings;
use feature qw{ say };
use Tk;
use Tk::Optionbox;

my $default_vsel = "Amazon";

my @options = (
    'option1',
    'option2',
    $default_vsel,
    'option4',
);

my $mw           = Tk::MainWindow->new(-title => 'Tk::Optionbox exampl
+e');
my $vsel         = $default_vsel;
my $variableFont = 'Arial';
my $newTop       = $mw->Frame->pack(-expand => 1, -fill => 'x');

my $selectVendor = $newTop->Optionbox(
                     -command  => \&select_vendor,
                     -textvar  => \$vsel,
                     -font     => $variableFont,
                     -options  => [@options],
                     -rows     => 15,
                   )->pack(-side=>'left');

Tk->MainLoop;


sub select_vendor {
    my $vendor = shift;
    say "Vendor is '$vendor'";
}
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