SQL>create or replace type number_array is table of number;
   2   /

Type created.

SQL>create or replace function str2tbl(p_str in varchar2, p_delim in varchar2 DEFAULT ',')
   2   return number_array
   3   as
   4     l_str  long default p_str || p_delim;
   5     l_n    number;
   6     l_data number_array := number_array();
   7   begin
   8     loop
   9       l_n := instr(l_str, p_delim);
  10       exit when(nvl(l_n,  0 ) =  0 );
  11       l_data.extend;
  12       l_data(l_data.count) := ltrim(rtrim(substr(l_str,  1 , l_n -  1 )));
  13       l_str := substr(l_str, l_n +  1 );
  14     end loop;
  15     return l_data;
  16   end;
  17   /

Function created.

SQL>var p_param varchar2( 30  char);
SQL>exec :p_param:='1,2,3,4,5';

PL/SQL procedure successfully completed.

SQL>select * from table(str2tbl(:p_param,','));

COLUMN_VALUE
------------
            1 
            2 
            3 
            4 
            5