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";
}                                                            

##</code><code>##

Beginning state: $c is not defined.
SV = NULL(0x0) at 0x1f5cec0
  REFCNT = 1
  FLAGS = ()


State after printing: $c is not defined.
SV = PV(0x1f3de10) at 0x1f5cec0
  REFCNT = 1
  FLAGS = ()
  PV = 0

0
State after integer operation: $c is not defined.
SV = PVNV(0x1f3c0d0) at 0x1f5cec0
  REFCNT = 1
  FLAGS = ()
  IV = 0
  NV = 0
  PV = 0

State after assignment: $c is defined.
SV = PVNV(0x1f3c0d0) at 0x1f5cec0
  REFCNT = 1
  FLAGS = (NOK,pNOK)
  IV = 0
  NV = 0
  PV = 0

State after assigning undef: $c is not defined.
SV = PVNV(0x1a0f0d0) at 0x1a2fec0
  REFCNT = 1
  FLAGS = ()
  IV = 0
  NV = 0
  PV = 0