{
        my %history;

        sub _log {
                my $self = shift;
                my $attrib = shift;
                my $value = $self->{$attrib};
                push @{ $history{$self} }, [ $attrib, $value ];
        }

        sub undo {
                my $self = shift;
                return unless (scalar @{ $history{$self} });
                my ($attrib, $value) = @{ pop @{ $history{$self} } };
                $self->{$attrib} = $value;
        }

 sub DESTROY {
  my $self = shift;
  delete $history{$self};
 }
}
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