...
my $can = $objects->Canvas(-relief  => "raised", -borderwidth => 2, -width => 225, height => 150)->place(-x => 5, -y => 180);
...

 my $node = Tk::GraphItems::TextBox->new(canvas => $can, text => 'test', x => 50, y => 50);

my $node = Tk::GraphItems->TextBox(canvas => $can, text => 'test', x => 50, y => 50);

Tk::GraphItems::TextBox->new 

(Tk::GraphItems::TextBox())->new 

'Tk::GraphItems::TextBox'->new 

use strict;
use warnings;
use Tk;
use Tk::GraphItems;
#require Tk::GraphItems;
use Tk::GraphItems::TextBox;

my $mw = tkinit;
my $c = $mw->Canvas->pack;

my $tb = Tk::GraphItems::TextBox->new(canvas => $c,
                        x => 10,
                        y => 20,
                        text => 'test');
MainLoop;

my $mw = new MainWindow(-title => "Robot Control GUI", -height => 600, -width => 800);
   my $objects = $leftframe->Frame(-relief  => "raised", -borderwidth => 2,-height => 350, -width => 250)->grid(-row => 1, -sticky => "nw");
  $objects->Label(-text => "OPTICAL OBJECT SETUP\n========================================")->place(-x => 0, -y => 0);

  $objects->Label(-text => "select object file:")->place(-x => 5, -y => 40);
  $selectobo = $objects->JComboBox(-choices => \@obolist)->place(-x => 120, -y => 40);
  $selectobo->setSelectedIndex(0);
  $objects->Button(-text => 'select for configuration', -command => sub {&config($selectobo)} )->place(-x => 67, -y => 70);
  $objects->Label(-text => '----------------------------------------------------------------------------')->place(-x => 5, -y => 92);
  $objects->Label(-text => "configuration for")->place(-x => 5, -y => 110);
  $objects->Entry(-relief => 'flat', -textvariable => \$cursel, -state => 'disabled', -width => 20)->place(-x => 95, -y => 110);
  $rb1 = $objects->Radiobutton(-text => '      active', -value => "active", -variable => \$obomode, -command => \&modeselect)->place(-x => 45, -y => 140);
  $rb2 = $objects->Radiobutton(-text => '      passive', -value => "passive", -variable => \$obomode, -command => \&modeselect)->place(-x => 45, -y => 160);
  $can = $objects->Canvas(-relief  => "raised", -borderwidth => 2, -width => 225, height => 150)->place(-x => 5, -y => 180);
  foreach (sort keys %{$oo})
  {
     my $node = Tk::GraphItems::TextBox->new(canvas => $can, text => 'test', x => 50, y => 50);
  }

#!/usr/bin/perl

use strict;
use warnings;
use Tk;
use Tk::GraphItems;

my $oo = { 1 => 'hallo', 2 => 'test', 3 => 'perl' };

my $mw = new MainWindow(-title => "Robot Control GUI", -height => 600, -width => 800);

  my $can = $mw->Canvas(-relief  => "raised", -borderwidth => 2, -width => 225, height => 150)->place(-x => 5, -y => 180); # ==
  foreach (sort keys %{$oo})
  {
     my $node = Tk::GraphItems::TextBox->new(canvas => $can, text => 'test', x => 50, y => 50);
  }

MainLoop;

while(1)
{
  print "HILFE\n";
}