package A;
use B;
use C;
use strict;

sub new {
	my ($class) = @_;
	bless {}, $class;
}

sub make_B {
	my ($self) = shift;
	return new B(@_);
}

sub make_C {
	my ($self) = shift;
	return new C(@_);
}

### and then, in my script...
use A;
my $a = A->new();
# $a has all the methods of A

my $b = $a->make_B('a', 'b');
# now $b has all the methods of B

my $c = $c->make_C('c', 'd');
# and $c has all the methods of C