I think your problem is that you're passing a reference to $TOK_IN to the start function, but then are making a copy of the variable as the object attribute $self->{tok_in}.  In your run method, you're then assigning some input value to the copy ($pokus->{tok_in}="hallo\n";), while IPC::Run is attempting to transfer (pump) input from the original variable $TOK_IN, which is still empty...

To avoid the problem, just set up the attributes before calling start, and pass \$self->{tok_in} instead of \$TOK_IN  (same holds for $TOK_OUT and $TOK_ERR):

  ...
  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";
[download]

Actually, you don't really need an extra $TOK_IN etc. at all — you can also just set the attributes to undef:  my $self = {tok_in => undef, ...