Okay, I think this will satisfy your needs. Backspace and delete still work in their standard left-to-right fashion, but otherwise I don't think there will be any problems.

#!/usr/bin/perl
# urdu.pl, written by Mike Foster
# feel free to reuse, modify, redistribute,
# bend, fold, staple, or mutilate.

use strict;
use warnings;
use Tk;

my $lastlength=1;
my $lastdepth=1;
my $mw = MainWindow->new(
    -background=>"darkviolet"
    );
$mw->title('Right-to-left text entry');

my $t1 = $mw->Text(
       -background=>"navy",
       -foreground=>"white",
       -height=>35,
       -width=>80,
       -wrap=>"word",
       -selectbackground=>"blueviolet"
       )->pack;
$t1->bind("<Key>" => \&rtl);

sub rtl {
    #gets end position
    my $depth = $t1->index('end');
    #reduces to line
    $depth =~ s/\..*$//;
    #converts back to an integer
    $depth--;
    if ($lastdepth < $depth) {
        $t1->SetCursor('insert - 1 lines lineend');
    }
    #remember where we were
    $lastdepth = $depth;
    
    #gets end of current line
    my $length = $t1->index('insert lineend');
    #reduces to character number
    $length =~ s/^.*\.//;
    #converts back to integer
    $length++;
    if ($lastlength < $length) {
        $t1->SetCursor('insert - 1 chars');
    }
    #remember where we were
    $lastlength = $length;
}

MainLoop;
[download]

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