Okay, I've played with the same Tcl module and demo as you did and found here are two ways of performing task: almost pure-tcl and reworked for perlTk syntax.

First one, bacically feeds original demo to Tcl interpreter, and starting MainLoop (remember you still have very easy access to Tk widgets with perlTk syntax...) 

use strict;
use Tcl::Tk;

my $mw = Tcl::Tk::tkinit;

$mw->interp->Eval(<<'EOS');
package require tkdnd

## Iconify ".". We are going to add windows and call update many times
+.
## Avoid some interesting visual effects :-)
wm withdraw .

#---------------------------------------------------------------------
+---------
#    Step 1: A simple Drag Source
#---------------------------------------------------------------------
+---------
# create the source window
label .source -text "source" -relief groove -bd 2 -width 20
pack .source -pady 5
# tells the DND protocol source can deliver textual data
dnd bindsource .source text/plain {return "testing DND"}
# bind the DND operation on left button
bind .source <1> {dnd drag %W}

#---------------------------------------------------------------------
+---------
#    Step 1: A simple Drop Target accepting plain text
#---------------------------------------------------------------------
+---------
# defines the target window
label .text_plain -text "drop plain text" -relief raised -bd 1 -width 
+20
pack .text_plain -pady 5
# Before registering a drop target, we always have to make sure the
# corresponding widget has been created:
update idle
# tells the DND protocol target can handle textual data
dnd bindtarget .text_plain text/plain <Drop> \
  {%W configure -text %D; status "\[target1\] type='%T', action='%A'"
   after 2000 {%W configure -text "drop plain text"}}


#---------------------------------------------------------------------
+---------
#    Step 2: Management of multiple types on the source
#---------------------------------------------------------------------
+---------

# defines an other type on source
dnd bindsource .source TK_COLOR {return "pink"}

# defines a target window
label .target2 -text "drop color" -relief raised -bd 1 -width 20 \
        -bg lightyellow
pack .target2 -pady 5

# tells the DND protocol target can handle color data
dnd bindtarget .target2 TK_COLOR <Drop> {
    status "\[target2\] type='%T', data='%D', action='%A'"
    .target2 configure -bg %D
    after 2000 ".target2 configure -bg lightyellow"
}

#=====================================================================
+=========
#    END
#=====================================================================
+=========

proc status {msg} {
    .status configure -text $msg
}

proc init {} {
    wm title . "Simple Drag & Drop Demo..."

    label .status -relief sunken -bd 1 -width 60 -anchor w
    pack .status -side bottom -fill x
    pack [frame .sep -height 10] -side bottom -fill x
    pack propagate .status 0
}

init
update
wm deiconify .
EOS

# Tcl inclusion for GUI finished here; you can work with widgets here 
+like:
#   my $lab = $mw->interp->widget('.status');
#   $lab->configure(-text=>'new text here...');

Tcl::Tk::MainLoop;

[download]

2nd method is reworked a bit to be more Perl-looking: 

use strict;
use Tcl::Tk;

my $mw = Tcl::Tk::tkinit;
my $interp = $mw->interp;

$interp->invoke('package', 'require', 'tkdnd');

## Iconify ".". We are going to add windows and call update many times
+.
## Avoid some interesting visual effects :-)
#wm withdraw .

#---------------------------------------------------------------------
+---------
#    Step 1: A simple Drag Source
#---------------------------------------------------------------------
+---------
# create the source window
my $lab_source = $mw->Label(-text=>"source", qw/-relief groove -bd 2 -
+width 20/)->pack(-pady=>5);
# tells the DND protocol source can deliver textual data
$interp->call('dnd','bindsource', $lab_source->path, 'text/plain', q{r
+eturn "testing DND"});
# bind the DND operation on left button
$interp->call('bind', $lab_source->path, '<1>', 'dnd drag %W');

#---------------------------------------------------------------------
+---------
#    Step 1: A simple Drop Target accepting plain text
#---------------------------------------------------------------------
+---------
# defines the target window
my $lab_text_plain = $mw->Label(-text=>"drop plain text", qw/-relief r
+aised -bd 1 -width 20/)->pack(-pady=>5);
# Before registering a drop target, we always have to make sure the
# corresponding widget has been created:
$interp->update('idle');
# tells the DND protocol target can handle textual data
$interp->call('dnd','bindtarget', $lab_text_plain, 'text/plain', '<Dro
+p>', \\'WDTA', sub {
    my (undef,$int,$sub) = (shift,shift,shift);
    my ($W,$D,$T,$A) = (@_); # Ev vars
    my $receiver_widget = $int->widget($W);
    $receiver_widget->configure(-text=>$D);
    status("[target1] type='$T', action='$A'");
    $int->after(2000, sub {$receiver_widget->configure(-text=>"drop pl
+ain text")});
    });


#---------------------------------------------------------------------
+---------
#    Step 2: Management of multiple types on the source
#---------------------------------------------------------------------
+---------

# defines an other type on source
$interp->call('dnd','bindsource', $lab_source->path, 'TK_COLOR', q{ret
+urn "pink"});

# defines a target window
my $lab_t2 = $mw->Label(-text=>"drop color", qw/-relief raised -bd 1 -
+width 20 -bg lightyellow/)
  ->pack(-pady=>5);

# tells the DND protocol target can handle color data
$interp->call('dnd','bindtarget',  $lab_t2, 'TK_COLOR', '<Drop>', , \\
+'WDTA', sub {
    my (undef,$int,$sub) = (shift,shift,shift);
    my ($W,$D,$T,$A) = (@_); # Ev vars
    $lab_t2->configure(-bg=>$D);
    status("[target1] type='$T', action='$A'");
    $int->after(2000, sub {$lab_t2->configure(-bg=>'lightyellow')});
    });
 

#=====================================================================
+=========
#    END
#=====================================================================
+=========


$interp->wm('title','.',"Simple Drag & Drop Demo...");

my $lab_stat = $mw->Label(qw/-relief sunken -bd 1 -width 60 -anchor w/
+)->pack(qw/-side bottom -fill x/);
$mw->Frame(-height=>10)->pack(qw/-side bottom -fill x/);

sub status {
    my $msg = shift;
    $lab_stat->configure(-text=>$msg);
}


$mw->update;

$interp->MainLoop;

[download]

Best regards,
Courage, the Cowardly Dog

In reply to Re: Tcl::Tk GUI working - Help with TkDnD through perl? by Courage
in thread Tk Drag and Drop Between Applications by Ardemus

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