use strict;
use warnings;
use 5.010;

$| = 1;

{
    package Dog;

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

my $dog = Dog->new();

print 'hello', 
      $dog->bark(), 
      undef $dog, 
      $dog->bark(), 
      'world',
;

--output:--
Bow wow!
Can't call method "bark" on an undefined value at 2.pl line 17.
destroy