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

my $top=MainWindow->new();
my $canvas=$top->Canvas(width=>300, height=>245)->pack();

my $origin_x=110;
my $origin_y=70;
my $PI=3.141592635;
my $circle_radius=5;
my $path_radius=0;
my $angle = 0;

&animate();

$top->Button(-text=> 'Again', -command=>\&animate)->pack;
            
MainLoop();

sub animate{

  $canvas->delete('circles');

  $origin_x=110;
  $origin_y=70;
  $circle_radius=5;
  $path_radius=0;
  $angle = 0;

  my $repeater;

  $repeater = $top->repeat(500,  sub{
        $path_radius+=7; 
        $circle_radius+=3; 
        $angle+=10;
    
        my $path_x=$origin_x+$path_radius*cos($angle*$PI/90);
    
        my $path_y=$origin_y-$path_radius*sin($angle*$PI/90);
    
        $canvas->create('oval', $path_x-$circle_radius,
                    $path_y-$circle_radius,
                    $path_x+$circle_radius,
                    $path_y+$circle_radius,
                    -fill=>'yellow',
                -tags => ['circles'],
                );
                    
       $canvas->create('line', $origin_x, $origin_y,
                    $path_x, $path_y,
                    -fill=>'slategray',
                -tags => ['circles'],
                );
    
    if( $angle > 180 ){ $repeater->cancel } 
    }
  );
}
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