Hi all, i have a Tk-program with a start-button and a stop-button to start or stop a pipe to an external programm. The start-botton works fine and start the pipe for the external-program. But if i click on the stop-button the program is hanging. I dont know how i can stop the pipe over the stop-button without hanging the program. The goal is to start or stop the pipe on every click on the certain button. May be anybody has an idea? It would be very very nice...

  use Tk;
#================================================
#        Main-Window
#================================================
  $HF = new MainWindow (-title => "Main-Window");
  $HF->geometry('100x100');

#==================================================
#        Buttons
#==================================================
  $BtnStart = $HF->Button
  (
  -text=>"START", 
  -command => \&ext,
  -borderwidth => 2,
  -relief => raised,
  )->pack();


  $BtnStop  = $HF->Button
  (
  -text=>"STOP  ",
  -command => sub{close (FH);$HF->update();},
  )->pack();

#================================================
# Tk-End
#================================================
  MainLoop();

#================================================
# SUB-Programs
#================================================
  sub ext
  {
        #xxxx Pipe to the external programm
    open(FH, "c:\\extern.exe |");

    while($tp=<FH>)
    {
        print "\n$tp";
        $HF->update();
    }
  }
[download]

best regards, michbach