That's normal behavior because the callback is called when the widget is first created and when each value is changed. The trick is to keep the callback down to the fewest possible values; hence the value can be modified by user interaction just like other widgets. Using an example from the source: 
#!/usr/bin/perl 

use strict;
use warnings;
use Tk;

my $top = MainWindow->new();
$top->title("scale tests");

my $f = $top->Frame(
    -relief => 'ridge', 
    -borderwidth => 3,
);

my $s = $top->Scale(
    "-orient" => "horizontal",
    "-length" => 300,
    "-from"   => 0,
    "-to"     => 250,
    "-tickinterval" => 25,
    "-command" => sub {
        my $s; 
        $f->configure(
            '-width' => $s->get
        ) 
    }
);

$s->pack(-side => 'left',  -fill => 'y');
$f->pack(-side => 'right', -fill => 'y');

Tk::MainLoop;

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In reply to Re: Tk::Scale, how to avoid callback when displayed? by Khen1950fx
in thread Tk::Scale, how to avoid callback when displayed? by perltux

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