# my.pl
use My::Factory;

my $obj = My::Factory->new('Apple');
...
# My/Factory.pm
package My::Factory;
1;
sub new{
  my $factoryclass = shift;
  my $class = "My::" . shift; # My::Apple
  my $filename = $class;
  $filename =~ s/::/\//g;  
  $filename .= '.pm'; # My/Apple.pm
  if ( -e $filename ) {
    require $filename;
  } else {
    die "not found: $filename";
  }     
}