Hi, sometimes with notebook, you have to use the -raisecmd option for the tabs. Here is a working version of your script. I just minimally hacked it to make it work, but it demonstrates the principle. You probably need to redesign the "add tabs" part , and put it in a loop, storing your data and objects in a hash. Anyways, this works, but needs improving. (I know this is'nt obvious, I happened to know it by previous hacking with notebook)

#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use Tk::Graph;
use Tk::NoteBook;

my $data = {
    Sleep  => 51,
    Work   => 135,
    Access => 124,
    mySQL  => 5
};

my $to_register = {
    'one'   => [ 0, 5, 4, 8, 6, 8 ],
    'two'   => [ 2, 5, 9, 4, 6, 2 ],
    'three' => [ 0, 5, 6, 8, 6, 8 ],
};

my $data1 = {
    'one'   => 3,
    'two'   => 3,
    'three' => 3,
};

my $mw = MainWindow->new;

my $nb = $mw->NoteBook(
    -ipadx => 10,
    -ipady => 10,
  )->pack(
    -side   => 'top',
    -expand => '1',
    -fill   => 'both'
  );

############# PAGE 1 ############# 


my $page1 = $nb->add( "page1",
               -label => " Page1 ",
               -raisecmd => sub{
                     $mw->update;
                 },
                );

my $graph = $page1->Graph( -type => 'BARS' )->pack(
    -expand => 1,
    -fill   => 'both'
);

$graph->configure( -variable => $data );

$graph->set($data);

############# PAGE 2 ############# 

my $graph1;
my $graph1_set = 0;
my $page2;
$page2 = $nb->add( "page2",
                -label => " Page2 ",
                -raisecmd => sub{
                   return if $graph1_set;
                   $graph1 = $page2->Graph(
                   -type => 'Line',
                   -max  => 10,
                   -look => 10,
                )->pack(
                      -expand => 1,
                      -fill   => 'both'
               );

            $graph1->register($to_register);
            $graph1->variable($data1);
            $mw->update;
            $graph1_set = 1;
                 }, );

MainLoop;
[download]