my $redo; # flag

sub status () {
  $SIG{USR1} = \&status;
  print STDERR "Currently running:  $StartedProcess\n";
  $redo = 1; # re-set flag
}

# Opens external program, and as long as it exists, checks
# if there is data in the pipe (STDOUT/STDERR)
sub createProcess () {
  my($line, $selector, @ready, $fh);

  $StartedProcess = open3(*CMD_IN, *CMD_OUT, *CMD_ERR, "./external.pp");
  close(CMD_IN);

  $selector = IO::Select->new();
  $selector->add(*CMD_ERR, *CMD_OUT);
  $redo = 1; # set flag
  while($redo) {
    $redo = 0; # clear flag
    while(@ready = $selector->can_read) {
      # do some operations on STDOUT/STDERR here
    }
    warn "after inner loop\n";
  }
  warn "closing CMD_OUT and CMD_ERR\n";
  close(CMD_OUT);
  close(CMD_ERR);
}