MainApp.pm
MyModel.pm
config

##</code><code>##

model:MyModel
option:Value

##</code><code>##

sub train {
    my ($himself, $training_data) = @_;
    my $option = $himself->{'option'};
    ...
}

##</code><code>##

sub new {
    my ($class, $conf_file) = @_
    my $options = read_conf($conf_file);
    # now $options == {model=>'MyModel',option=>'Value'}
    eval "require $options->{model}";
    return bless $options, $class;
}
sub train_model {
    my ($self, $raw_data) = @_;
    my $data = do_magic_with($raw_data);

    #Either:
    no strict 'refs';
    &"$self->{model}::train"($self, $data);

    #Or:
    my $model = $self;
    bless $model, $self->{'model'};
    $model->train($data);

    #Or:
    {
        local @ISA = $self->{model};
        $self->train($data);
    }
}