use strict;
use warnings;
use Tk; 
use Tk::DragDrop; 
use Tk::DropSite; 
use Tk::HList;

my $mw = new MainWindow; 
my $hlist = $mw->Scrolled('HList', -scrollbars => "osoe")->pack(-side 
+=> "left", -expand => 1, -fill => 'both'); 
my $cnt = 0;
foreach (sort keys %ENV)
    {
    $hlist->add($cnt);
    $hlist->itemCreate($cnt, 0, -text => $_);    
    $cnt++;
    }
my $token = $hlist->DragDrop(-event        => '<B1-Motion>', 
                                -sitetypes    => ['Local'], 
                                -startcommand => \&StartDrag); 
$hlist->DropSite(-droptypes     => ['Local'], 
                       -dropcommand   => [\&Drop, $hlist, $token]); 
MainLoop; 

sub StartDrag { 
   my $w = $token->parent; 
   my $e = $w->XEvent; 
   my $idx = $w->nearest($e->y); 
   print "Drag Y: " . $e->y . "\n"; 
   print "Pos: $idx\n"; 
   if (defined $idx) { 
      $token->configure(-text => $w->itemCget($idx, 0, -text)); 
      my($X, $Y) = ($e->X, $e->Y); 
      $token->MoveToplevelWindow($X, $Y); 
      $token->raise; 
      $token->deiconify; 
      $token->FindSite($X, $Y, $e); 
   } 
} 

sub Drop { 
   my $w = $token->parent; 
   my $e = $w->XEvent; 
   my $idx = $w->nearest($e->y); 
   print "Drop Y: " . $e->y . "\n"; 
   print "Pos: $idx\n"; 
}
[download]

Case matters! The drop coordinates are X, Y, not x, y!
لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

When i chance the x to X and y to Y the Drag and Drop functions report both the false idx... With lower case the Drag function returns the right idx but the drop return the same idx :-(