package MyClass::A;
use strict;
use warnings;
use Exporter;
use base qw(Net::Server::PreFork);
#our @ISA = qw(Exporter);
our @EXPORT = qw(new serve);
our @EXPORT_OK = qw();

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

  #...
  return $self;
}

sub process_request
{
    #...
}

sub serve
{
    my ($self) = @_;
    MyClass::A->run();
    return $self;
}


my $s = MyClass::A->new();
$s->serve();