my %make_a = qw(
  Calvin::Hobbes new
  Peter::Gabriel play
  Dog::Day::Afternoon watch
);
...
if (my $constructor = $make_a{$class_name}) {
  unless ($INC{$class_name}) {
    eval "require $class_name"; die $@ if $@;
  }
  $object = $class_name->$constructor();
}