use Tk;
use strict;

my $i;
my @var1;
my $var2;
my $status;

my $mw = MainWindow->new; 

#fill @var1 with zeros...
for ($i = 0; $i <= 81; $i++) {$var1[$i] = 0;}

#Do a similar thing with $var2
$var2 = 0;

my $frame_01 = $mw->Frame(-background=>'grey')->pack(-side=>'top', -fill => 'x');
my $frame_12 = $mw->Frame(-background=>'grey')->pack(-side=>'top', -fill => 'x');
my $frame_13 = $mw->Frame(-background=>'grey')->pack(-side=>'top', -fill => 'x');
my $frame_14 = $mw->Frame(-background=>'grey')->pack(-side=>'top', -fill => 'x');
my $frame_15 = $mw->Frame(-background=>'grey')->pack(-side=>'top', -fill => 'x');

$i = 1;
$frame_01->Label(-text => "$i:",                 -width=>2, -relief => 'flat')   ->pack(-side =>'left');
$frame_01->Entry(-textvariable => \$var1[$i++],  -width=>2, -relief => 'sunken') ->pack(-side =>'left');
$frame_01->Entry(-textvariable => \$var1[$i++],  -width=>2, -relief => 'sunken') ->pack(-side =>'left');
$frame_01->Entry(-textvariable => \$var1[$i++],  -width=>2, -relief => 'sunken') ->pack(-side =>'left');
$frame_01->Label(-text => " ",                   -width=>1, -relief => 'raised') ->pack(-side =>'left');
$frame_01->Entry(-textvariable => \$var1[$i++],  -width=>2, -relief => 'sunken') ->pack(-side =>'left');
$frame_01->Entry(-textvariable => \$var1[$i++],  -width=>2, -relief => 'sunken') ->pack(-side =>'left');
$frame_01->Entry(-textvariable => \$var1[$i++],  -width=>2, -relief => 'sunken') ->pack(-side =>'left');

$frame_12->Button(-text => "var1 1",      -command => sub { change_var1_1(@var1); })         ->pack(-side => 'left'); 
$frame_12->Button(-text => "var1 2",      -command => sub { @var1 = change_var1_2(@var1); }) ->pack(-side => 'left'); 
$frame_12->Button(-text => "CHG var1 3",  -command => sub { $var1[3] = 2;})                  ->pack(-side => 'left'); 
$frame_12->Button(-text => "CHG var1 5",  -command => sub { $var1[5] = 7;})                  ->pack(-side => 'left'); 

$frame_13->Button(-text => "var2 1",      -command => sub { change_var2_1($var2); })         ->pack(-side => 'left'); 
$frame_13->Button(-text => "var2 2",      -command => sub { $var2 = change_var2_2($var2); }) ->pack(-side => 'left'); 
$frame_13->Button(-text => "CHG var2",    -command => sub { $var2 = 3;})                     ->pack(-side => 'left'); 

$frame_14->Label(-text => "var1[3] is:",      -relief => 'flat')                           ->pack(-side =>'left');
$frame_14->Label(-textvariable => \$var1[3],  -relief => 'flat')                           ->pack(-side =>'left');
$frame_14->Label(-text => ", var1[5] is:",    -relief => 'flat')                           ->pack(-side =>'left');
$frame_14->Label(-textvariable => \$var1[5],  -relief => 'flat')                           ->pack(-side =>'left');
$frame_14->Label(-text => ", var2 is:",       -relief => 'flat')                           ->pack(-side =>'left');
$frame_14->Label(-textvariable => \$var2,     -relief => 'flat')                           ->pack(-side =>'left');

$frame_15->Label(-text => "Status", -relief => 'flat')                                     ->pack(-side =>'left');
$frame_15->Label(-textvariable => \$status,  -relief => 'flat')                            ->pack(-side =>'left');

MainLoop();

sub change_var1_1 {
    @var1 = change_var1_2(@var1);
    $status = "change_var1_1 called $var1[3], $var1[5]";
}
sub change_var2_1 {
    $var2 = change_var2_2($var2);
    $status = "change_var1_1 called $var2";
}

sub change_var1_2 {
    my @lv_1 = @_;

    $lv_1[3] = 6;
    #$var1[3] = 6; # this works if you uncomment it
    $status = "change_var1_2 called $lv_1[3]";
    return(@lv_1);
}

sub change_var2_2 {
    my $lv_2 = @_[0];

    $lv_2 = 6;
    $status = "change_var2_2 called $lv_2";
    return($lv_2);
}