x1 is a tosmabru word.
This is a Lojban-specific concept. A “tosmabru word” is a sequence of characters which looks like a lujvo, but it falls apart into several cmavo and a lujvo/gismu. For details see https://mw.lojban.org/papri/tosmabru_test . See also valslinku'i. Note: You probably should use lo'u/le'u or zoi to quote x1, as zo will probably not work here.