package MyApp::BaseClass;

sub new {
    my $class = shift;
    my $init_args = shift;

    # a real example would have warnings etc. here.
    ref $init_args eq 'HASH' || $init_args = {};

    my $self = { _init => $init_args };
    bless $self, $type;

    # self is re-assigned to allow the _init to replace itself
    $self = $self->_init() ||
                 UsefullErrorObject->new({ class => $class, args => $init_args });

    return $self;
}

sub _init {
    my $self = shift;

    # subclass this
    # first hashref argument to new() is in $self->{_init}

    return $self;
}