use warnings;
use strict;
use Tk;
use Tk::Button;
use Tk::Checkbutton;
use Tk::LabEntry;
use Tk::Label;

my $cmdLineText;
my $mw=MainWindow->new(-title=>'Foo Installer');
my $row = 0;

my $w_install = $mw-> Button ( -overrelief=>'raised', -relief=>'raised', -text=>'Install', -command=>\&installItems) -> grid(-column=>0, -row=>++$row, -columnspan=>3, -sticky=>'nsew');

my $w_cmdWindow = $mw->Label (-height=>7, -foreground=>'white', -background=>'black', -textvariable => \$cmdLineText)->grid(-column=>0, -row=>++$row, -columnspan=>3, -rowspan=>10, -sticky=>'nsew');

MainLoop;
sub installItems {
  open (FILE, "cmd.exe /c dir|");    #does something
  $cmdLineText = "";
  while (<FILE>) {
    #chomp;
    $cmdLineText .= $_;
  }
  close(FILE);
}