An interesting note:

If we insert some 'print' statements, we can see that the $dlg->add() function resets the value of $id, I am assuming because it does not match any of the 'valid' options.

#... code 

    my $id = $sel || (@ids && $ids[0]) || '';
    
    print "id 1 is <$id>\n";

    my $IDText = $dlg->add (
        'JComboBox',
        -mode => 'readonly',
        -selectcommand => [\&changeEditPlayer, \$id],
        -validate => 'match',
        -textvariable => \$id,
        );
    
    print "id 2 is <$id>\n";
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What is also interesting, is that we cannot set $id to anything now that is associated with the readonly JComboBox. However, once the options are defined, $id can be set, but only to a valid option.

    $id = "Joe";print "id is not Joe!! <$id>\n";

    $IDText->form (-left => '%0', -right => '%100', -top => '%0');
    $IDText->configure (-options => \@ids);

    # not only sets the selection but calls <c>changeEditPlayer</c>

    $id = "Joe"; print "now id is not empty!! <$id>\n";

    # does nothing, because 'Sandy' is not a valid option

    $id = "Sandy"; print "id not set to Sandy because it is an invalid
+ option <$id>\n";

    $id = $sel || (@ids && $ids[0]) || '';
    
    ### now it works !!

    $IDText->setSelected ($id); # dosn't work
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With the print statement modified slightly in changeEditPlayer, we get the following results (without any clicking of the mouse!)

id 1 is <Fred>
id 2 is <>
id is not Joe!! <>

 - inside changeEditPlayer Joe

now id is not empty!! <Joe>
id not set to Sandy because it is an invalid option <Joe>

 - inside changeEditPlayer Fred
[download]

Honestly, I was a bit confused when I was first playing with this bit of code. Never had I seen a straight declaration, like the following, not work.

$id = 'Sandy';
print "<$id>\n";  # prints Joe
[download]