From a design point of view, this looks like a task for Module::Pluggable. If all your modules A, B, C, D provide similar interface, you could just iterate over $self->plugins in your methods instead of spelling out special cases for A, B, C, D manually. Untested pseudo-Perl example:

package Synergy;

use Module::Pluggable instantiate => 'new';

sub new {
 my ($class, @opts) = @_;
 return bless [ $class->plugins(@opts) ], $class;
 # now your object contains objects of classes A, B, C, D
 # and whatever else was in Synergy/*.pm near Synergy.pm
}

sub process {
 my ($self, @args) = @_;
 return map { $_->process(@args) } @$self;
 # passes args to all sub-modules
}
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On the other hand, if your modules all provide different methods with no intersection whatsoever and you just need to have all of them in one class, you could try to use base to inherit all their methods automatically. This way you only need to spell out your parent packages once.

But if you need to call different parent methods from the same method depending on other circumstances... That sounds like a very complex wrapper. Maybe what you are trying to achieve can be achieved in a simpler way?