Here are a couple of simple scripts to help get you going. The script below just shows a simple thread which can do the stepper control, without blocking the gui. The important point is that the main Tk thread, will not be able to update textvariables automatically from the thread. So you need a timer running, to check the shared vars, and set the textvariables to their values. And as a bonus, here is a link which should show you how to make graphic of the motor position. See Tk compass dial. You could make one with 2 arrows, one for setting the motor, and a second for displaying the feedback position.

Simple thread with feedback:

#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use threads;
use threads::shared;

my $go : shared;
my $die : shared;
my $step_set : shared;
my $feedback : shared;
$go = 0;
$die = 0;
$step_set = 0;
$feedback = 0;

my $repeater;
my $stepper = 0;
my $feedback_display = 0;
my $thread = threads->new(\&work);

my $mw = MainWindow->new( -title => "Stepper Test" );

my $entry = $mw->Entry(-textvariable => \$stepper)->pack();
my $indicator = $mw->Label(-textvariable => \$feedback_display)->pack(
+);

$mw->Button(-text=>'Start Stepper',
            -command=> sub {
                 $step_set = $stepper;                 
             $go = 1;
         
                 # timer to read shared vars
         $repeater = $mw->repeat(10,sub{
                  $feedback_display = $feedback;
              
              if( $feedback_display == $stepper){   
                      $go =0;
                      }
                  });
         
          
         })->pack();

$mw->Button(-text=>'Exit',
            -command=> sub {
                  $go = 0;
          $die = 1;   # must return before joining
              $repeater->cancel;
                  # JOIN ALL THREADS 
                    foreach my $thread (threads->list) { 
                     $thread->join;                                   
+        
                   }
                  exit;
          })->pack();


MainLoop;

sub work{
    $|++; 
    while(1){
       if($die == 1){ return }; 
      
       if ( $go == 1 ){
         
           for(0..$step_set){
             print "$_\n";
             $feedback = $_;
         select(undef,undef,undef,.5);
            }
  
       }else
         { sleep 1 }
    }

}
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