# in My::Package
sub operater_on_all_data
{
    my $value;
    my $i = 0;
    foreach ( @internal_data_storage ) {
       $helper = $i++;
       $value += &user_sub_variable( $i++ );
    }
}

# in user_sub
sub user_sub {
    my $multiplier = shift;
    return $_ * 2 * $multiplier;
}