A thought: the translation layers should not just map classes, but should be able to add/detect useful metadata. For instance in translating Perl errors into Ruby or Python, it may be good to allow a Perl type to translate into a Ruby Class, and a Ruby Class to translate into a Perl Class with some extra metadata tagged on it (so that it falls into a type that would be translated back). This piece of complexity allows you to do as reasonable a job as is realistically possible in translating between 2 class hierarchies that divided things up in fundamentally incompatible ways.

Yes, this kind of approach would make those interfaces substantially more complex. But I think that the complexity is necessary.

A tangential thought that this discussion of translation brings to mind. I think that it is important for the Perl world to plan on some "best practices" for handling internationalization. (Documentation, error messages, etc.) The current CPAN works great..if you're willing to say that all programmers must speak English fluently. But I'm convinced that many people with scripting problems do not speak English as a first language, and I'd like to think that Perl will attempt to address their problems.

Definition of alomorph:

A variant phonological representation of a morpheme; "the 
final sounds of `bets' and `beds' and `horses' and `oxen' 
are allomorphs of the English plural morpheme"
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UPDATE:

For those without ancient languages... greek and latin roots. Basically morph is shape, allo is "different" or "another".

Another definition for allomorph seems a bit closer to Larry's reply: "An allomorph is one of two or more complementary morphs which manifest a morpheme in its different phonological or morphological environments."

So, I guess in the computer context, an allomorph is an object that manifests differently depending on the context.

I was using "allomorph" neither in the linguistic sense you quoted, nor in the crystalographic sense you omitted, but in the more general sense of "an abstract object that can manifest different shapes in different contexts." When you read a dictionary entry with two related but specific meanings, you really ought to expect that those meanings are allomorphs of a single underlying meaning, especially when that general meaning is easily derived from the meanings of the Greek morphemes in question.