First of all, in Tk (or any gui program) using "sleep" will block the gui, so it's a "no-no". But to show you how to make it work ,in terms of your question, you need to set $|=1 and update your text widget after each print. Like:

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

$|=1;

my $mw = tkinit;

# a frame in my Tk main window 
my $frame = $mw->Frame;

# a text widget with attached scrollbars in my frame 
my $OutputText = $frame->Scrolled('Text',
   -height => '10',
      -width => '50',
         -scrollbars => 'osoe'
         );

         # pack frame and text widget 
         $frame->pack(qw/-side left -fill y/);
         $OutputText->pack(qw/-side bottom -fill both -expand 1/);

         # here I try to tie STDOUT to the text widget 
         my $widget = $OutputText->Subwidget("text");
         tie *STDOUT, ref $widget, $widget;

$mw->Button(-text=>'start', -command => [\&start])->pack;;

MainLoop;

sub start{

for ( 1..10 ) {
   sleep 1;
      print "foo\n";
      $OutputText->update;
      }

}
__END__
[download]

But here is probably a better way, without using sleep. The reason is that a repeat loop, lets the Tk event loop proceed, and respond to the gui, while sleep will block everything until it is done.

#!/usr/bin/perl
use warnings;
use strict;

use Tk;

my $mw = MainWindow->new();
my $tx = $mw->Text()->pack();

tie *STDOUT, 'Tk::Text', $tx;

$mw->repeat(1000, \&tick);

MainLoop;

my $count;
sub tick {
 ++$count;
 print "$count\n";
}
[download]

However, you don't say what you are ultimately trying to do, and tie'ing STDOUT in Tk is not done very often, because there are usually better ways to accomplish it, like printing directly to the text box. What kind of program are you trying to make?

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.