Hi, here is another variation which is simple to see what happens.

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

my $mw = tkinit;
$mw->geometry('200x200+200+200');
$mw->overrideredirect(1);
my %wdraginfo;


$mw->bind('<ButtonPress-1>', sub{ 
   my $xe = $mw->XEvent;
   $wdraginfo{xoff} = $mw->pointerx - $mw->rootx;
   $wdraginfo{yoff} = $mw->pointery - $mw->rooty;
    });

        
$mw->bind('<B1-Motion>', sub{ 
  my ($x,$y);
  $x=$mw->pointerx-$wdraginfo{xoff};
  $y=$mw->pointery-$wdraginfo{yoff};
        
  $mw->geometry($mw->width."x".$mw->height."+$x+$y");
         });

MainLoop;
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