You might want to look at MooseX::AttributeHelpers. It lets you create handlers for hashrefs and arrayref types (among other types), something like this (based on the example in the documentation):

  has 'options' => (
      metaclass => 'Collection::Hash',
      is        => 'rw',
      isa       => 'HashRef[Str]',
      default   => sub { {} },
      provides  => {
          exists    => 'option_exists',
          kv        => 'options',
          get       => 'get_option',
          set       => 'set_option',
          clear     => 'clear_options',    
          accessor  => 'option', 
      },
      curries  => {
          set       => { set_quantity => [ 'quantity' ] }
      }
  );
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This lets you use the get_option and set_option methods, or option to use accessor syntax like $obj->option('test') to get an option or $obj->option( test => 'value') to set the value, and clear_options clears the whole hash. The curries hash lets you pass parameters to the handler methods in object methods, e.g. $obj->set_quantity(42) (using the code above) would be equivalent to $obj->set_option(quantity => 42)

See MooseX::AttributeHelpers::MethodProvider::Hash for the options available for hash objects.