use Tk;

my $mw = tkinit;
my $label = $mw->Label(-text => 'Ok', 
       -relief => 'sunken', 
       -width => 30, 
       -height => 30)->pack();
$mw->Button(-text => 'resize', -command => [\&res,$label])->pack();
$label->packPropagate(0);

MainLoop;

sub res{
  my ($label) = @_;
  $label->configure(-height => 40, -width => 40);
}