feature liga {
     lookup liga1 {
     sub f l by f_l;        #f_l glyph does not exist
     sub f i by f_i;
     sub f f by f_f;
     sub f f l by f_f_l;
     sub f f i by f_f_i;
     sub xddde by a;        #xdde glyph does not exist
     sub [a b] by c;
     } liga1;
 } liga;
