G'day jsteng,

To the best of my knowledge, you cannot do this with Tk::Entry; however, you can code this functionality with Tk::Text.

The following code is fully functional. It shows how to set up the pseudo-entry widget (note the initial text has no spaces; just 12345). The "Latest Entry" button will retrieve the full, possibly edited, text (note the chomp) and update the display above.

#!/usr/bin/env perl

use strict;
use warnings;

use Tk;

my $mw = MainWindow::->new(-title => 'Vertical Entry');
$mw->geometry('300x400+40+40');

my $string = '12345';
my $entry = $mw->Text(-width => 1, -wrap => 'char');
$entry->pack(-fill => 'y', -side => 'left');
$entry->insert('1.0', $string);
$mw->Label(-textvariable => \$string)
    ->pack(-fill => 'x', -side => 'top');
$mw->Button(-text => 'Latest Entry', -command => sub {
    chomp($string = $entry->get('1.0', 'end'))
})
    ->pack(-fill => 'x', -side => 'top');
$mw->Button(-text => 'Exit', -command => sub { exit })
    ->pack(-side => 'bottom');

MainLoop;
[download]

It looks pretty weird to me, but that's what you asked for. :-)