...
  my $self = {tok_in => $TOK_IN, tok_out => $TOK_OUT, tok_err => $TOK_ERR, tok_program => $tok_program};

  $self->{tok} = start [ $tok_program, @tok_param ], 
                       '<',      \$self->{tok_in}, 
                       '1>pty>', \$self->{tok_out}, 
                       '2>',     \$self->{tok_err},  debug => 2
      or die "Can't exec program: $?;\n";