#!/usr/bin/perl -w
use strict;

use Tk;
use Tk::NoteBook;

my $MW = MainWindow->new();
my $note = $MW->Label(-font=>'courier-12',-text=>
        "F1-4 presents/withdraws the notebook windows.")->pack();

my (@VW, @NB, %pg, %txt);
foreach (0..3) { 
        my $title = eval("$_+1"); 
        $VW[$_] = $MW->Toplevel(-title=>"$title"); $VW[$_]->state('withdrawn');
        $NB[$_] = $VW[$_]->NoteBook()->pack();
        foreach my $L ("A","B","C","D") { my $name = "$L-$title";
                $pg{$name} = $NB[$_]->add($name,-label=>'empty'); 
        }   
}
foreach (keys %pg) {$txt{$_} = $pg{$_}->Text()->pack()}
#       this version causes a seg fault:
#foreach (keys %pg) {$txt{$_} = $pg{$_}->Text(-font=>"courier-12")->pack()}
$MW->bind('all',"<Key-F1>"=>sub{toggle(0)});
$MW->bind('all',"<Key-F2>"=>sub{toggle(1)});
$MW->bind('all',"<Key-F3>"=>sub{toggle(2)});
$MW->bind('all',"<Key-F4>"=>sub{toggle(3)});

MainLoop;##################

sub toggle { my $n = "@_";
        my $state = $VW[$n]->state();
        my $newstate = ($state eq 'withdrawn') ? 'normal' : 'withdrawn';
        $VW[$n]->state("$newstate");
}