I have a mainwindow with three buttons: 
#!/usr/bin/perl -w 
                                                                      
+   
use Tk;
use strict; 
                                                                    
my $mw = MainWindow->new;     

    my $var=0;

    my $button_A = $mw->Button( 
    -text    => '  Button A', 
    -command =>[\&rutine, $var, ]);#
    $button_A->pack; 
    
    my $button_B = $mw->Button( 
    -text    => ' ++ ', 
    -command => sub{$var++;  print"\$var is $var!\n";});
    $button_B->pack; 
    
    my $button_C = $mw->Button( 
    -text    => ' -- ', 
    -command => sub{$var--; print"\$var is $var!\n";});
    $button_C->pack; 
    
MainLoop;


sub rutine
{
    my ($var)=@_;
    
    print "$var\n";

}

[download]
Button A prints the value of variable $var. Button '++' increments $var and Button '--' decrements $var. However if I first increment $var with '++' and then want to print its value with "Button A" the value of $var is 0 why is this? I guess I have missed something fundamental is it so? Thank you for your help.

In reply to Fundamental tk-problem by tamaguchi

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