Use of uninitialized value in print at...

##</code><code>##

Can't call method "exterminate" on an undefined value at (eval 2) line 1.

##</code><code>##

#! perl
use strict;
use warnings;
use 5.010;

$| = 1;
my $num = 42;

{
    package Dog;

    sub new     { return bless {}; }
    sub bark    { say 'Bow wow!'; }
    sub DESTROY { print "destroy\n"; ++$num; }
}

my $dog = Dog->new();

print 'hello ', 
      $dog->bark(),
      undef $dog, 
      eval('$dog->bark()'),
      "|$num|",
      "world\n";

print $num;

##</code><code>##

18:02 >perl 552_SoPW.pl
Bow wow!
Use of uninitialized value in print at 552_SoPW.pl line 31.
hello 1|42|world
destroy
43
18:02 >