#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my @SLIDERVALUES = (0,0,0,0);
my @slider;
my $i;

sub show_array {
print "\@SLIDERVALUES = ($SLIDERVALUES[0], $SLIDERVALUES[1], $SLIDERVALUES[2], $SLIDERVALUES[3])\n";
}

# window setup 
my $mw = MainWindow->new;

foreach my $i (0 .. 3) {
  $slider[$i] = $mw->Scale(
      -from    => 30,
      -to    => 0,
      -orient    => 'vertical',
      -variable    => \$SLIDERVALUES[$i],
 #     -command => undef,
     )->pack(-side    => 'left');
}

show_array();

# This breaks things! 
@SLIDERVALUES = (5, 10, 15, 20);

show_array();
slider_update(); 

$SLIDERVALUES[0] = 7;
$SLIDERVALUES[1] = 14;
$SLIDERVALUES[2] = 21;
$SLIDERVALUES[3] = 28;

show_array();
slider_update(); 

$mw->update;
MainLoop;

############################################# 
sub slider_update{
  foreach my $i (0 .. 3) {
     $slider[$i]->set( $SLIDERVALUES[$i] );
   }
}