# here's what I mean, I hacked your example
# the trip button adds a third element, which gets dropped
# silently. (and you can escape it, and see the escape...

use Tkx;
$Tkx::TRACE = 64;
Tkx::package_require('tile');
my $mw = Tkx::widget->new(".");
my $list;

my @strings;
$strings[0] = 'Hello, this should be ok';
$strings[1] = 'this too';

$list = &make_tcl_list(@strings);


# example bug : new_tk__listbox
( $lb = $mw->new_listbox( -height => 5,-listvariable => \$list ) )
  ->g_grid( -column => 0, -row => 0, -sticky => "nwes" );
(
    $s = $mw->new_ttk__scrollbar(
        -command => [ $lb, "yview" ],
        -orient  => "vertical"
    )
)->g_grid( -column => 1, -row => 0, -sticky => "ns" );
$lb->configure( -yscrollcommand => [ $s, "set" ] );
(
    $mw->new_ttk__label(
        -text   => "Status message here",
        -anchor => "w"
    )
)->g_grid( -column => 0, -row => 1, -sticky => "we" );
( $mw->new_ttk__sizegrip )->g_grid( -column => 1, -row => 1, -sticky => "se" );
$mw->g_grid_columnconfigure( 0, -weight => 1 );
$mw->g_grid_rowconfigure( 0, -weight => 1 );

## add a button to add an unbalanced brace
(my $button = $mw->new_tk__button(
   -text=>"Trip",
   -anchor=>'w',
   -command=> sub {
      $strings[2] = 'watch this{';
      $list=&make_tcl_list(@strings);
      }
      ))->g_grid( -column => 0, -row => 1, -sticky => "nwes" );


Tkx::MainLoop();


sub make_tcl_list{
   my @LIST = @_;

   my $listx = ''; 
   for my $i (@LIST) {
      $listx = $listx . ' {' . $i . '}';
   }
   return $listx;
}