OK, OK, the help says that for Character strings, no transform is performed. :)
Yup, I see what you mean. I think that has to do with the fact that the lengths of the masks and the lcAPN values are different. But that still sounds like an undocumented feature.

This was part of my test. If the alphas and numerics are switched, they both return .T.

lcAPN = "123456A-B789012C-D345678EF-GH901234I-KLMNOP"
?(lcApn= TRANSFORM(lcAPN, "999999X-X999999X-X999999XX-XX999999X-XXXXXX"))
lcAPN = "ABCDEF1-2DEFGHI3-4JKLMNO56-78PQRSTU9-012345"
?(lcApn= TRANSFORM(lcAPN, "999999X-X999999X-X999999XX-XX999999X-XXXXXX"))

>Strange, but these are my tests:
>lcAPN = "123456A-B789012C-D345678EF-GH901234I-KLMNOP"
>?(lcApn= TRANSFORM(lcAPN, "999999X-X999999X-X999999XX-XX999999X-XXXXXX"))
>lcAPN = "a123456A-B789012C-D345678EF-GH901234I-KLMNOP"
>?(lcApn= TRANSFORM(lcAPN, "999999X-X999999X-X999999XX-XX999999X-XXXXXX"))
...
>
>Undocumented feature?