I have a module A which has multiple features B, C, D, because multiple people will work on these and it would be nice to have this logical separation of the different features.

That's not the way you should design object-oriented code.

You should find useful abstractions based on how they interact with each other, not by who develops them.

It's not making use of any OO concepts

That might be an indicator that you don't actually need any OO - how about just a hash with objects B, C, D? Or a sub that returns those objects, based on the argument you pass to it?

The existence of shiny OO tools don't mean you have to use them for every case.

What doesn't your current solution do that you might want from it? Extensibility? You can still stick other objects in the attributes if you make them writable (a hash provides that by default).

sub another_method {
    my ($self) = @_;
    $self->a->exec(...); # Stuff related to C
}
[download]

Looks like delegation would make your life easier here.

But in general it is very hard to give advise based on such general descriptions. It could be anything from "Don't use OO at all" to "use delegation" or "use roles" or "stick with your current approach" - we just don't have enough context to decide.