# lib/Animal.pm

package Animal;

sub new {
  my $class = shift;
  return bless {}, $class;
}

sub is_furry {
  my $self = shift;
  warn "We don't know if this animal is furry or not!\n";
  return undef;
}

sub make_noise {
  my ( $self, $noise ) = @_;
  print $noise, "\n";
}

1;

# lib/Bear.pm

package Bear;

use base 'Animal';

# We know bears are furry, so override Animal's is_furry method:
sub is_furry {
  my $self = shift;
  return 1;
}

sub eat_honey {
  my $self = shift;
  # Make use of Animal's make_noise method:
  $self->make_noise( "Yum!" );
}

1;

# example.pl

use Animal;
use Bear;

my $baloo = Bear->new;
if ( $baloo->is_furry ) {
  $baloo->eat_honey;
}