use Tk;

my $mw = MainWindow->new;

my %btns;
for (qw(alpha beta gamma)){
    my $name = $_;
    $btns{$_} = $mw->Button(
        -text => $_,
        -command => sub{foo($name)},
        )->pack;
}

MainLoop;

sub foo{

    my $name = shift;
    for (keys %btns){
        $btns{$_}->configure(-state => 'disabled');
    }

    my %dispatch =(
        alpha => \&alpha,
        beta => \&beta,
        gamma => \&gamma,
        );

    $dispatch{$name}->($name);

    for (keys %btns){
        $btns{$_}->configure(-state => 'normal');
    }
}

sub alpha{
    print "alpha\n";
    sleep 4;
}
sub beta{
    print "beta\n";
    sleep 4;
}
sub gamma{
    print "gamma\n";
    sleep 4;
}