• indeed, you need interpreter to make any Tcl/Tk operations.
• at any time $widget->interp returns it
• at any time $widget->path returns widget path in the form .fr.t stringification should also work so "$widget" should return path;
• Tcl::Tk and Tk widgets are very interchangeable, and here lies the extreme power of approach. Say, you have existing GUI, you can write $button=widget('.fr.b'); and then just use $button with perl/Tk syntax
• to make Tcl/Tk calls, you should go either of following ways:
  1. $interp->Eval('package require tkdnd');
  2. $interp->invoke('package', 'require', 'tkdnd');
  3. $interp->call('package', 'require', 'tkdnd');
  1st one allows you to execute any Tcl/Tk code, 2nd is much faster than all of them because there is no parsing or substitution, 3rd one is most generic and most frequently used and it allows for you to directly use anonymous subroutines, scalar references and so on...

  It could be a bit confusing that Tcl uses curly braces in a very different way compared to Perl (those are string delimeters w/o interpolation) but you do not need to go into Tcl syntax really deep.

  What you wrote

  $i -> call("dnd bindsource", ".perl_hlist_object", "text/uri", {\&Perl
  +_Sub});
  $i -> call("bind", ".perl_hlist_object", "<1>", {dnd drag %W};
  [download]

  should probably be

  $i -> call("dnd", "bindsource", ".perl_hlist_object", "text/uri", \\'%
  +W',sub{Perl_Sub(shift)});
  $i -> call("bind", ".perl_hlist_object", "<1>", 'dnd drag %W');
  [download]

Also use Tcl::Tk discussion list tcltk-perl at lists.sourceforge.net

addition 1 Please refer to documentation of Tcl.pm module using perldoc Tcl, or may be http://search.cpan.org/~vkon/Tcl-0.84/Tcl.pm, so there are plenty explanations of 'call', 'icall', 'invoke' methods

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]

Courage & Monks,

I'm just getting back from winter break (and I hope you had a good holiday). Thank you so much for all of your advice and input! With your extensive help I got the application working prior to leaving for holiday.

My DnD implementation is now five by five.

Thanks again,

Ardemus

But be sure to read my post in meditations section related to this! (at Perl is able to deal with Drag-n-Drop within Tk and another applications)

and few final words: with Tcl::Tk, as opsed to perlTk, you can get more and with more flexibility,
but be prepared to some surprises, which are hopefully not hard to solve....

Best regards,
Courage, the Cowardly Dog