use Tk;
use strict;

my $Main = MainWindow->new();
my $Frame = $Main->Frame();
$Frame->pack();
my $Button1 = $Frame->Button(-text=>'One', -command=>\&one);
$Button1->pack();
my $Button2 = $Frame->Button(-text=>'Two', -command=>\&two);
$Button2->pack();
my $Button3 = $Frame->Button(-text=>'Three', -command=>\&three);
$Button3->pack();
my $Button4 = $Frame->Button(-text=>'Four', -command=>\&four);
$Button4->pack();

MainLoop();

sub one() {
print "Hello\n";
}

sub two() {
$Button1->configure(-state => "disabled");
print "State Disabled: Only Button Three Can Enable Not Button Four.\n"
}

sub three() {
$Button1->configure(-state => "normal");
print "State Normal\n";
}

sub four() {
$Button1->configure(-state => "normal");  
print "State Normal\n";
}