use strict;
use warnings;
use feature 'say';

package OO;
sub new {my $animal = $_[1]; return bless \$animal;}
sub species { return ${$_[0]} }

package main;
my $cat = 'cat';
my $dog = 'dog';

my $self = new OO( $cat );
{
    my $self = $self;
    $self = new OO( $dog ) if $ARGV[0] eq 'Fido';
    say $self->species();
}
say $self->species();