$Tkx::TRACE = 64;
use Tkx;
...
## create button
my $b = $mw->new_ttk__button(
    -text => 'Hello, world',
    -command => sub { $mw->g_destroy; },
);
$b->g_pack;

## retrieve existing button by name (button created using Tkx::eval())
## my $b = Tkx::widget->new(".b");

## Tkx::i::call(".b", "configure", "-background", "blue");
## Tkx::eval(".b configure -background blue");
$b->configure( -background => "blue")