sub foo {
  my ($self, $data) = @_;
  $self->{bar} = _some_function($data);
}

##</code><code>##

sub _some_function {
  my ( $self, $data ) = @_;
  return ParentClass::_some_function($data);
}

##</code><code>##

#!/usr/bin/perl -w
use strict;
use Data::Dumper;
package Foo;

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

sub foobared {
   my $self = shift;
   $self->{foo} = _test( 3 );
}

sub _test { shift }

package Bar;
@Bar::ISA = 'Foo';
sub foobared {
   my $self = shift;
   $self->{foo} = $self->_test( 3 );
}

package Main;
my $o = Foo->new;
$o->foobared;
print $o->{foo},$/;
my $o2 = Bar->new;
$o2->foobared;
print $o2->{foo};

##</code><code>##

3
Bar=HASH(0xa065cc8)