f
f-Latn
fr-Latn-F
a-value
en-a-bbb-a-ccc     # 'a' appears twice 
tlh-a-b-foo
i-notexist          # grandfathered but not registered: invalid, even if we only test well-formedness
abcdefghi-012345678
ab-abc-abc-abc-abc
ab-abcd-abc
ab-ab-abc
ab-123-abc
a-Hant-ZH
a1-Hant-ZH
ab-abcde-abc
ab-1abc-abc
ab-ab-abcd
ab-123-abcd
ab-abcde-abcd
ab-1abc-abcd
ab-a-b
ab-a-x
ab--ab
ab-abc-
-ab-abc
ab-c-abc-r-toto-c-abc  # 'c' appears twice