Second background process is pausing the gui

[Ohad]

Hi, I'm using perl/Tk. I've created a background process to run a cmd and I want the main process to continue working. This is fine and works, until I invoke an additional background process. Than the GUI is stuck until the first process is done.

This is the first background process:

 open (my $st_in, "<&STDIN");
    open (my $out, '>&', STDOUT);
    open (my $err, '>&', STDERR);
    open (STDOUT, "> /dev/null");
    open (STDERR, "> /dev/null");
    open (STDIN, "< /dev/null");
    my $status = open ($reg_out,"$cmd 2>&1 |") or die "can't fork: $!"
+;
    if ($status)    #Parent
    {
        open (STDOUT, '>&', $out);
        open (STDERR, '>&', $err);
        open (STDIN,  '<', $st_in);
    }
    else
    {
        exit;
    }
    $Reg_r{$regl_name}{$nn}{'OutP'} =$reg_out;
    $Reg_r{$regl_name}{$nn}{'PID'} = $status;
    $Reg_r{$regl_name}{$nn}{'JobId'} = 0;
    $Reg_r{$regl_name}{$nn}{'IsRun'} = 1;
    $Reg_r{$regl_name}{$nn}{'WasRuning'} = 0;
    $book->raise("Sheet 1") if ($re_run_csv);
    $Sbook->raise("$regl_name $nn");
    $mw->fileevent($reg_out, 'readable', [\&fill_text_widget,$regl_nam
+e,$nn]);

Second can be anything, a simple xterm

 system("xterm -e '$viewer $log' &")

Any idea how to solve it? So the main process will not be stuck? As you see in the code, I tried many options, exec/system/`,I tried closing STDs.. Could really use some advice here