OK here is a complete test case. Note that shift right mouse will drag an item from the list box to the entry but will not drag the selected word to the entry from the text widget. The problem seems to be that I cannot grab back the binding to shift right mouse (i.e. <Shift-3>) from the text widget, so the event to DragDrop gets ignored or is never seen by DragDrop.

#!perl
use Tk;
use Tk::Text;
use Tk::DragDrop;
use Tk::DropSite;

$mw=MainWindow->new;
$entry=$mw->Entry()->pack(-expand=>1);
$f=$mw->Frame->pack();
$text=$f->Text()->pack(-anchor=>'e');
$text->bind('<Shift B3>');
$text->bind('<Shift B3-Motion>',sub {print "Moving\n"});
$list=$f->Listbox()->pack(-anchor=>'w');
foreach (qw(one two three four)) {$list->insert('end',$_)}
$text->insert('end',"now is the time for all good perl monks\nto drag 
+and drop.");
$dnd_token2 = $list->DragDrop
  (-event     => '<Shift B3-Motion>',
   -sitetypes => ['Local'],
   -startcommand => sub { $main::dnd_token=$dnd_token2;StartDrag($main
+::dnd_token,$text) },
  );
    $dnd_token1 = $text->DragDrop
    (-event     => '<Shift B3-Motion>',
     -sitetypes => ['Local'],
     -startcommand => sub { $main::dnd_token=$dnd_token1;StartDrag1($m
+ain::dnd_token,$text) },
     );
    # Define the target for drops.
    $entry->DropSite
    (-droptypes     => ['Local'],
     -dropcommand   => [ \&Drop, $entry, \$main::dnd_token ],
     );

sub StartDrag1 {

    my($token,$text) = @_;
    my $w = $token->parent; # $w is the source text widget
    my $e = $w->XEvent;
# then the search string is whatever is selected, if anything
    my(@sel,$txt);
    if (@sel=($text->tagRanges('sel'))[0..1]) {
    $txt=$text->get(@sel);
    }
    if (defined $txt) {
        # Configure the dnd token to show the listbox entry
        $token->configure(-text => $txt);
        # Show the token
        my($X, $Y) = ($e->X, $e->Y);
        $token->MoveToplevelWindow($X, $Y);
        $token->raise;
        $token->deiconify;
        $token->FindSite($X, $Y, $e);
    }
}

sub StartDrag{

    my($token,$text) = @_;
    my $w = $token->parent; # $w is the source listbox
    my $e = $w->XEvent;
    my $idx = $w->nearest($e->y); # get the listbox entry under cursor
    if (defined $idx) {
        # Configure the dnd token to show the listbox entry
        $token->configure(-text => $w->get($idx));
        # Show the token
        my($X, $Y) = ($e->X, $e->Y);
        $token->MoveToplevelWindow($X, $Y);
        $token->raise;
        $token->deiconify;
        $token->FindSite($X, $Y, $e);
    }
}

sub Drop {
# Accept a drop and insert a new item in the destination listbox.
    my($lb, $dnd_source) = @_;
    $dnd_source=$$dnd_source;
    $lb->insert("end"," ") if ($lb->get ne '');
    $lb->insert("end", $dnd_source->cget(-text));
}
MainLoop();
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