dual monitor on/off

#!/usr/bin/perl -w
use strict;
use Gtk2 '-init';
mk_main_window();
Gtk2->main;
sub mk_main_window {
    my $mw = Gtk2::Window->new;
    $mw->signal_connect (destroy => \&close_this_app );
    $mw->set_title ("Monitors");
    my $vbox0 = Gtk2::VBox->new();
    $mw->add($vbox0);
    my $b1 = Gtk2::Button->new("Turn Second Monitor ON");
    $b1->signal_connect(clicked=> \&turn_monitor_on);
    $vbox0->add($b1);
    my $b3 = Gtk2::Button->new("Turn Second Monitor OFF");
    $b3->signal_connect(clicked=> \&turn_monitor_off);
    $vbox0->add($b3);
    $mw->show_all();
}
sub turn_monitor_on {
    system("xrandr --output VGA-0 --auto --output DVI-I-0 --auto --right-of VGA-0");
    close_this_app();
}
sub turn_monitor_off {
    system("xrandr --output DVI-I-0 --off");
    close_this_app();
}
sub close_this_app {
    Gtk2->main_quit;
}