in reply to Creating dynamic parent/child relationships

May not be appropriate, but you can use the if pragma to conditionally load a module.

use if $some_condition, Three;
(That's page 1019 in the Fourth Edition of The Camel, in case you have a dead tree version, which I do.)

Alex / talexb / Toronto

Thanks PJ. We owe you so much. Groklaw -- RIP -- 2003 to 2013.