You mean the feature of connected boxes? I did say it is a feature, not a bug. And you can use it by creating an array and using a reference to it as a -choices parameter. For example:

my @array= ('1', '2','123');

my $box1 = $Screen->JComboBox( ... , -choices= \@array );
my $box2 = $Screen->JComboBox( ... , -choices= \@array );
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As long as you use a reference to the same array, the boxes are in sync to the first box, the master. At least that's how I understood the documentation.