It depends. If you don't need to interact with the program you are calling, just open it as a piped file handle.

use warnings;
use strict;
use Tk;

my $top = MainWindow->new;

my $text = $top->Scrolled('Text', -scrollbars => 'se')->pack;

my @commands = ('dir', "type $0", 'ping 127.0.0.1');


for my $command(@commands){
  open my $fh, '-|', $command;
  while (my $line = <$fh>){
      $text->insert('end', $line);
      $text->see('end');
      $text->update;
  }
  $text->insert('end', "\n".('=' x 79)."\n");
}

MainLoop;
[download]

Update: Never mind, this doesn't do what you were asking. If there is already a console window open, this won't open a new one, however, if you suppress the console window on start with wperl, it will open one. Sigh.