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


my $data = 'whatever';

# do whatever here to print to STDOUT or xterm

# or
# to display the Tk

if (fork == 0) {
    my $top = new MainWindow;
    $top->geometry('200x200+100+100');
    
    $top->Label( -text=> $data )->pack();
    
    
    $top->Button(
         -text => 'Exit',
         -command => sub { exit })->pack;
    MainLoop;
    
    CORE::exit();
   }

# always do your forks first, before creating Tk in the main script
# my $mw = new MainWindow; 
# MainLoop;  # not needed in this example

# non Tk script t can continue here
for (1.. 3){

  print "$_\n";
  sleep 1;
 }

exit;

#If you need start a new process from one of the child processes, then
#you have to establish some kind of IPC (e.g. pipes) between the child
#and parent.

#I the launched task running another Perl/Tk module or function or a
#complete new program? In the latter case, you should just use fork and
#exit/system and do not forget to use CORE::exit instead of exit in the
#child process (according to the FAQ). Perl/Tk forks are somewhat more
#difficult. You have to make sure that you fork off the process which
#does not have a created a MainWindow itself. This will work fine: