Parent class:

package Parent;

use strict;
use warnings;
use Class::MethodMaker
    new_hash_init => 'new',
    get_set       => [qw( color )];

sub init {
    my $self = shift();
    print STDERR "initializing parent\n";
    my %values = @_;
    $self->color($values{color});
}

1;
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Child class:

package Child;

use strict;
use warnings;
use Class::MethodMaker
    new_hash_init => 'new',
    get_set       => [qw( shape )];

use base qw( Parent );

sub init {
    my $self = shift();
    my %values = @_;
    $self->SUPER::init(color => ($values{color}));
    $self->shape($values{shape} || 'square');
}

1;
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Main program:

use strict;
use warnings;
use Parent;
use Child;

my $p = new Parent(color => 'green');
my $c = new Child(shape => 'round', color => 'red');

print $p->color(), "\n";
print $c->color(), ", ", $c->shape(), "\n";
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