Okay, after doing some researching, reading and testing this is where I'm at with this ...

Firstly, thanks zentara for the article, that was helpful. I also read through a tonne of other articles and code, even read through the Tk::ExecuteCommand module source code which was fantastic. Its all helped ratify my understanding and clarify certain aspects. The TK::ExecuteCommand module manages to achieve what I'm hoping to. So let me summise the problem and progress made so far....

The first of your two examples above uses a call to startpiper(). I found his wasn't necessary and didn't make a difference, not sure if that was strategically intentional or just something written in by yourself. Surprisingly in my testing before writing this thread I'd written two very similar examples as the ones you did. Seems we went down similar paths. But your code helped clarify a few things also. So thanks mate.

To help exaggerate the issue I face and show the type of problem I'm describing you'll see in the code below I've change the "ls -la" to "ls -laR c:". This attempts a much bigger call, freezing up the gui while it processes. Okay, so lets get into the juice of this theory and see if we can nut it out...

The "fileevent" call binds itself to the "fill_text_widget" subroutine when the "CHILD" filehandle becomes "readable". Because this is a piped stream if you do a blocking (<>) call on it you'll freeze the gui. It requires reading the stream in bite size pieces and updating the text widget bit by bit. My code below demonstrates this based on code from the "TK::ExecuteCommand" and one I found in another manual. Interestingly, MOST INTERESTINGLY, my gui still freezes .... but something quite strange happens!! If I grab the window bar across the top of the window and move the window you can see it rapidly processing and appending the directory listing to the text box. Also I included a "bell" into the subroutine, and you can hear it looping through, and with the bell it doesn't freeze - at each bell the screen updates. WHY???!!!! Is the gui having troubles keeping up with the refresh? This is what I'm not sure of.

So, any help is appreciated on this bit.

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

open(CHILD, "ls -laR h: |") or die "Can't open: $!";

my $mw = new MainWindow;
my $t = $mw->Scrolled("Text",-width => 80, -height => 25, -wrap => 'no
+ne');
$t->pack(-expand => 1);
CHILD->autoflush(1);
$mw->fileevent('CHILD', 'readable', [\&fill_text_widget, $mw]);
$mw->after(500);
MainLoop;

sub fill_text_widget {
    my ($widget) = @_;
    if (eof(CHILD)) {
        $widget->fileevent('CHILD', "readable", undef); # cancel bindi
+ng
    return ;
    }
    if (sysread ('CHILD', $_, 4096)) {
        $t->insert('end', $_); # Append the data read
    $t->yview('end');
    $mw->bell;
    } else {
        # sysread returned undef. Problem with file
        $t->insert('end', "ERROR !!!"); 
        $widget->fileevent('CHILD', "readable", undef); # cancel bindi
+ng
    }
}
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