There is some documentation error of “CVX Users’ Guide”, the detailed information is as follows:
http://web.cvxr.com/cvx/doc/quickstart.html#other-norms-and-functions
[A quick start] Section → [Other norms and functions] SubSection:
Should replace “x_l1 = xzz(1:n,: ) - xzz(n+1:end,:);” with "x_l1 = xzz(1:n,: ) "