you can use a brutal method like storing all buttons into an hash:

my $mw = MainWindow->new;

my %buttons;

for (1..9){
           $buttons{$_} = $mw->Button(-text=>"Button $_",-command=>[\&
+colorize,$_])->pack;
}

MainLoop;

sub colorize{
             $buttons{$_[0]}->configure(-bg=>'yellow');
             print $buttons{$_[0]}->cget('-text')," button is yellow n
+ow\n";
}
[download]

Or you can use Canvas tagging facility to select the current one

L*