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

my $mw = MainWindow->new;

# the window must be mapped for a global grab
# so make a 1 pixel window in lower right corner
# for invisible grabs

$mw->geometry('200x200+50+50');
$mw->overrideredirect(1);

$mw->bind("<Key>", [  \&process_key_press , Ev('K')  ] );
$mw->bind("<KeyRelease>", [ \&process_key_release , Ev('K')  ] );

$mw->Label(-text=>"Press escape to exit")->pack();

$mw->after(100,sub{$mw->grabGlobal;});
$mw->focusForce;

MainLoop;

sub process_key_press{
  my ($caller, $key) = @_;
   print "Press $key\n"; 
   if ($key eq 'Escape'){exit}
}

sub process_key_release{
  my ($caller, $key) = @_;
   print "Release $key\n"; 
}