use strict; use warnings;

use Glib 'TRUE', 'FALSE';
use Gtk3 -init;

#new window and box
my $window = Gtk3::Window->new ('toplevel');
my $box = Gtk3::Box->new( 'vertical', 0);

my $notebook = Gtk3::Notebook->new();

# ----> works : append a new page in the notebook
my $n = Gtk3::Label->new('TABNAME');
my $c = Gtk3::Label->new('TABCONTENT');
$notebook->append_page ($c, $n);

my $btn = Gtk3::Button->new('Add page');
$btn->signal_connect('clicked' => sub {
    # ----> same code does nothing when called from a signal callback sub
    my $n = Gtk3::Label->new('TABNAME');
    my $c = Gtk3::Label->new('TABCONTENT');
    $notebook->append_page ($c, $n);
                     });

#add and show widgets
$box->pack_start($notebook, TRUE, TRUE, 0);
$box->add($btn);
$box->set_size_request (500, 300);
$window->add($box);
$window->show_all;

Gtk3::main;