The following script is an basic attempt at simulating a Windows 8 (WinRT, Metro, etc...) application GUI.
The main features are fullscreen only, no chrome, and a top and bottom app bar that are displayed when the cursor (or finger on touch screens) is at the top/bottom of the screen, and hidden otherwise.

I have used text labels on the "app bars" for demonstration purposes, a real app would have buttons that do things in place of the text labels.

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

#create a new MainWindow
my $mw = MainWindow->new( -background => 'black' );

#fullscreen
$mw->geometry($mw->screenwidth.'x'.$mw->screenheight);

#remove window chrome
$mw->overrideredirect(1);

#create a Tk::Frame to act as the top app bar hotspot.
my $top_appbar = $mw->Frame( -background => $mw->cget(-background), -h
+eight => 10 )->pack( -side => 'top', -fill => 'x' );
$top_appbar->bind('<Any-Enter>' => sub { \&AppBar($top_appbar, 'show',
+ 'top'); } );
$top_appbar->bind('<Any-Leave>' => sub { \&AppBar($top_appbar, 'hide',
+ 'top'); } );

#create a Tk::Frame to act as the bottom app bar hotspot
my $bottom_appbar = $mw->Frame( -background => $mw->cget(-background),
+ -height => 10 )->pack( -side => 'bottom', -fill => 'x' );
$bottom_appbar->bind('<Any-Enter>' => sub { \&AppBar($bottom_appbar, '
+show', 'bottom'); } );
$bottom_appbar->bind('<Any-Leave>' => sub { \&AppBar($bottom_appbar, '
+hide', 'bottom'); } );

#create a Tk::Frame to hold the application's content
my $content = $mw->Frame( -background => $mw->cget(-background), -heig
+ht => $mw->screenheight-20 )->pack( -fill => 'x' );
$content->Label( -text => 'This is where the application content is di
+splayed (buttons, images, etc...)', -background => $mw->cget(-backgro
+und), -foreground => 'gray' )->pack();

sub AppBar {
    my $self   = shift;
    my $method = shift;
    my $name   = shift;
    if ($method eq 'show'){
        #change the appbar's height and color to make it visable and u
+seable
        $self->configure( -background => 'gray' );
        $self->configure( -height => 50) if $name eq 'top';
        if ( $name eq 'top' ){
            $top_appbar->{label1} = $top_appbar->Label( -text => 'The 
+navigation bar, or top app bar, is the recommended place to put navig
+ation controls that let the user access other areas of the app (butto
+ns).', -background => 'gray', -foreground => 'black' )->pack( -side =
+> 'left' );
        } elsif ( $name eq 'bottom' ){
            $bottom_appbar->{label1} = $bottom_appbar->Label( -text =>
+ 'The bottom app bar is the recommended place to put commands (button
+s).', -background => 'gray', -foreground => 'black'  )->pack( -side =
+> 'left' );
            $self->configure( -height => 50);
            $mw->configure( -height => $mw->screenheight-60 );
        }
    } elsif ($method eq 'hide'){
        #change the appbar's height and color to make it hidden and no
+t useable
        $self->configure( -background => $mw->cget(-background) );
        $self->configure( -height => 10) if $name eq 'top';
        if ( $name eq 'top'){
            $top_appbar->{label1}->packForget();
        } elsif ( $name eq 'bottom' ){
            $bottom_appbar->{label1}->packForget();
            $self->configure( -height => 10 );
            $mw->configure( -height => $mw->screenheight-20 );
        }
    }
    $mw->update();
}

$mw->MainLoop();
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