ax-TZ # Not in the registry, but well-formed fra-Latn # ISO 639 can be 3-letters # fr-fra # Extended tag not in registry but we don't currently test that # fr-Lat # Extended tag not in registry but we don't currently test that fra fra-FX abcd-Latn # Language of 4 chars reserved for future use AaBbCcDd-x-y-any-x # Language of 5-8 chars, registered zh-Latm-CN # Typo de-DE-1902 # Wrong variant fr-shadok # Variant ab-c-abc-r-toto-c-abc # 'c' appears twice en-a-bbb-a-ccc # 'a' appears twice xr-lqt-qu # extlang + region (not in registry)