Add {expr} to the list of matches. Only to be used by the function specified with the 'completefunc' option. Returns 0 for failure (empty string or out of memory), 1 when the match was added, 2 when the match was already in the list. See |complete-functions| for an explanation of {expr}. It is the same as one item in the list that 'omnifunc' would return. Can also be used as a |method|: GetMoreMatches()->complete_add()