use strict;                                                  
use warnings;                                                
use Devel::Peek;                                             
                                                             
no warnings 'uninitialized';                                 
                                                             
my $c;                                                       
                                                             
is_defined('Beginning state: $c is ', $c);                   
Dump($c);                                                    
                                                             
print "\n$c\n";                                              
is_defined('State after printing: $c is ', $c);              
Dump($c);                                                    
                                                             
print "\n", (0 + $c), "\n";                                  
is_defined('State after integer operation: $c is ', $c);     
Dump($c);                                                    
                                                             
$c = 0 + $c;                                                 
is_defined("\nState after assignment: \$c is ", $c);         
Dump($c);                                                    

$c = undef;                                              
is_defined("\nState after assigning undef: \$c is ", $c);
Dump($c);                                                
                                                             
sub is_defined {                                             
    my ($msg, $value) = @_;                                  
    print $msg, (defined $value ? '' : 'not '), "defined.\n";
}