PLSQL variable assignment

Pass to a variable 10001,10002 This style is used to query , But at present, it will report an error , Please advise !

-- Data preparation
create table wareinfo(WareID number(5),WareName varchar(50));
insert into wareinfo values(10001,'A goods ');
insert into wareinfo values(10002,'B goods ');

select * from wareinfo;

-- Query statement
declare var_WareID varchar2(100) ;
var_WareName varchar2(100);
var_WareCursor sys_refcursor;
begin
var_WareID:='10001,10002';
open var_WareCursor for
--select wareinfo.WareName from wareinfo where WareID in (10001,10002) ;
select wareinfo.WareName from wareinfo where WareID in (var_WareID) ; -- Get the equivalent statement of the previous sentence through variables , But at present, it will report an error , Please advise !
fetch var_WareCursor into var_WareName;
while var_WareCursor%found loop-- Traversal cursor
dbms_output.put_line(var_WareName);
fetch var_WareCursor into var_WareName;
end loop;
end;