This is an interesting gottya that made me lose a day's development effort amd think I was going mad to boot. I have two objects declared from one class. One of the objects redefines a method e.g.: 
#!/usr/local/bin/perl -w
use strict;


my $class1 = shortTest->new('One');
my $class2 = shortTest->new('Two');

$class1->getName();
$class2->getName();

$class1->updateName();

$class1->getName();
$class2->getName();

package shortTest;
use strict;
1;

sub new {
  my $class = shift;
  my ( $name ) = @_;

  my $self  = {};
  bless $self, $class;

  $self->{name} = $name;

  *getName = \&showName;

  return $self;
}

sub showName {
  my $self = shift;

  print "$self->{name}:In 1st cut\n";
}

sub updateName {
  my $self = shift;

  *getName = \&showName2;
}


sub showName2 {
  my $self = shift;

  print "$self->{name}:In 2nd cut\n";
}

[download]
Having thought about it, I'm not sure this isn't "expected behaviour" – except it wasn't expected by me through hours of debugging :( I've had experience in OO languages (large amounts of Delphi plus some C++ and Java) but I didn’t mess about with the vtable in them very much. I had imagined that each object had it’s own vtable. Clearly that is not the case – or is someone going to tell me that I'm even dimmer than I already feel?

In reply to Redefining methods in non-singletons nearly drove me mad today by bangers

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