print 'My enemy must ', $enemy->obey(),
       undef($enemy),
      '. His phaser is named ', $phaser->{name},
       eval('$enemy->exterminate()'),
      ". Bye!\n"; 

##</code><code>##

*** Before print statement ***

$enemy------------------------->Dalek:{phaser=> + } (ref=1)
                                                |
                                +---------------+
                                v
$phaser------------------------>Phaser:{name=> + } (ref=2)
                                               |
                                +--------------+
                                v
                                'Exterminator' (ref=1)

argument stack:  -empty-

*** After print setup, before print executes ***

$enemy------------------------->Dalek:{phaser=> + } (ref=2)<-+
                                                |            |
                                +---------------+            |
                                v                            |
$phaser------------------------>Phaser:{name=> + (ref=2)     |
                                               |             |
                                +--------------+             |
                                v                            |
                                'Exterminator' (ref=2)       |
                                ^                            |
                                +--------------+             |
argument stack:  '. Bye!\n'                    |             |
                 eval('$enemy->exterminate()'  |             |
                 ref---------------------------+             |
                 '. His phaser is named '                    |
                 undef($enemy)                               |
                 obey()<-ref---------------------------------+
                 'My enemy must '

##</code><code>##

*** Executing through print, just after undef step ***

$enemy--->undef                 Dalek:{phaser=> + } (ref=1)<-+
                                                |            |
                                +---------------+            |
                                v                            |
$phaser------------------------>Phaser:{name=> + (ref=2)     |
                                               |             |
                                +--------------+             |
                                v                            |
                                'Exterminator' (ref=2)       |
                                ^                            |
                                +--------------+             |
argument stack:  '. Bye!\n'                    |             |
                 eval('$enemy->exterminate()'  |             |
                 ref---------------------------+             |
                 '. His phaser is named '                    |
                 undef($enemy)                               |
                 obey()<-ref---------------------------------+
                 'My enemy must '

##</code><code>##

*** Print just finished, now removing items from stack ... ***

$enemy--->undef                 Dalek:{phaser=> + } (ref=1)<-+
                                                |            |
                                +---------------+            |
                                v                            |
$phaser------------------------>Phaser:{name=> + (ref=2)     |
                                               |             |
                                +--------------+             |
                                v                            |
                                'Exterminator' (ref=1)       |
                                                             |
argument stack:  obey()<-ref---------------------------------+
                 'My enemy must '

##</code><code>##

$enemy--->undef                 Dalek:{phaser=> + } (ref=0)<-+
                                                |            |
                                +---------------+            |
                                v                            |
$phaser------------------------>Phaser:{name=> + (ref=2)     |
                                               |             |
                                +--------------+             |
                                v                            |
                                'Exterminator' (ref=1)       |
                                                             |
argument stack:  obey()<-ref---------------------------------+
                 'My enemy must '

##</code><code>##

$enemy--->undef                 Dalek:{phaser=>   } (ref=0)<-+
                                                             |
$phaser------------------------>Phaser:{name=> + (ref=1)     |
                                               |             |
                                +--------------+             |
                                v                            |
                                'Exterminator' (ref=1)       |
                                                             |
argument stack:  obey()<-ref---------------------------------+
                 'My enemy must '

##</code><code>##

$enemy--->undef                 {FREE MEMORY              }

$phaser------------------------>Phaser:{name=>'Exterminator'} (ref=1)

argument stack:  'My enemy must '

##</code><code>##

#!/usr/bin/perl              
use Data::Dumper;            
use Devel::Peek;             
{        
    package Foo;             
    sub new {                
        my $class = shift;   
        my $val = shift;     
        return bless { thing=>$val };      
    }    
         
    sub val {                
        my $self = shift;    
        return "val: " . (++$self->{theVal});
    }    
         
    sub DESTROY {            
        print "destroyed at ", ${shift}->{theVal}, "\n";
    }    
}        
         
my $b = [ ];                 
my $t = Foo->new($b);        
         
print "--- before print ---\n";  
Dump($b); Dump($t);          
print "--- Do the print ---\n";  
print   $t->val(),           
        Dump($b), Dump($t),  
        undef($t),           
        Dump($b), Dump($t), ".\n";
print "--- after print ---\n";
         
Dump($b);
Dump($t);

##</code><code>##

$ perl ex_destructo.pl
--- before print ---
SV = RV(0x8c650b4) at 0x8c650a8
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  RV = 0x8c47818
  SV = PVAV(0x8c4886c) at 0x8c47818
    REFCNT = 2
    FLAGS = ()
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)
SV = RV(0x8c650a4) at 0x8c65098
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  RV = 0x8c476f8
  SV = PVHV(0x8c4fa64) at 0x8c476f8
    REFCNT = 1
    FLAGS = (OBJECT,SHAREKEYS)
    STASH = 0x8c650c8	"Foo"
    ARRAY = 0x8c719d0  (0:7, 1:1)
    hash quality = 100.0%
    KEYS = 1
    FILL = 1
    MAX = 7
    RITER = -1
    EITER = 0x0
    Elt "thing" HASH = 0x20b61f7d
    SV = RV(0x8c65054) at 0x8c65048
      REFCNT = 1
      FLAGS = (ROK)
      RV = 0x8c47818
      SV = PVAV(0x8c4886c) at 0x8c47818
        REFCNT = 2
        FLAGS = ()
        ARRAY = 0x0
        FILL = -1
        MAX = -1
        ARYLEN = 0x0
        FLAGS = (REAL)
--- Do the print ---
SV = RV(0x8c650b4) at 0x8c650a8
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  RV = 0x8c47818
  SV = PVAV(0x8c4886c) at 0x8c47818
    REFCNT = 2
    FLAGS = ()
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)
SV = RV(0x8c650a4) at 0x8c65098
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  RV = 0x8c476f8
  SV = PVHV(0x8c4fa64) at 0x8c476f8
    REFCNT = 1
    FLAGS = (OBJECT,OOK,SHAREKEYS)
    STASH = 0x8c650c8	"Foo"
    ARRAY = 0x8c6b8d0  (0:6, 1:2)
    hash quality = 125.0%
    KEYS = 2
    FILL = 2
    MAX = 7
    RITER = -1
    EITER = 0x0
    Elt "theVal" HASH = 0x90484e39
    SV = PVIV(0x8c5b04c) at 0x8cd6348
      REFCNT = 1
      FLAGS = (IOK,POK,pIOK,pPOK)
      IV = 1
      PV = 0x8cd17e0 "1"\0
      CUR = 1
      LEN = 4
    Elt "thing" HASH = 0x20b61f7d
    SV = RV(0x8c65054) at 0x8c65048
      REFCNT = 1
      FLAGS = (ROK)
      RV = 0x8c47818
      SV = PVAV(0x8c4886c) at 0x8c47818
        REFCNT = 2
        FLAGS = ()
        ARRAY = 0x0
        FILL = -1
        MAX = -1
        ARYLEN = 0x0
        FLAGS = (REAL)
SV = RV(0x8c650b4) at 0x8c650a8
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  RV = 0x8c47818
  SV = PVAV(0x8c4886c) at 0x8c47818
    REFCNT = 2
    FLAGS = ()
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)
SV = RV(0x8c650a4) at 0x8c65098
  REFCNT = 1
  FLAGS = (PADMY)
val: 1.
destroyed at 
--- after print ---
SV = RV(0x8c650b4) at 0x8c650a8
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  RV = 0x8c47818
  SV = PVAV(0x8c4886c) at 0x8c47818
    REFCNT = 1
    FLAGS = ()
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)
SV = RV(0x8c650a4) at 0x8c65098
  REFCNT = 1
  FLAGS = (PADMY)