This is the language code for "multiple languages". Under normal circumstances, there should not be a test wiki here.
|multiple languages Wikibooks
This test was rejected by the Language Committee and has been deleted.
|This test wiki was rejected by the Language Committee and has been deleted. There could be an XML file available (ask here) which can be transferred to a non-Wikimedia wiki.|
||Test wiki content
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The language code "mul" is valid, strictly speaking, but a multilingual Wikibooks has been rejected twice by the Language Committee.