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 now\n";
}