with w0 as
(
select 1 as col1, '2,3,4,66,342,5' as col2 from dual union all
select 2 as col1, '1' as col2 from dual union all
select 3 as col1, '4,5,2,8,99,1' as col2 from dual
)
select  distinct w0.*
  from  w0,
        xmltable(
                 col2
                 columns
                   x number path '.'
                ),
        xmltable(
                 '&p_str'
                 columns
                   y number path '.'
                )
  where x = y
/
Enter value for p_str: 1,99
old  15:                  '&p_str'
new  15:                  '1,99'

      COL1 COL2
---------- --------------
         2 1
         3 4,5,2,8,99,1

SQL> /
Enter value for p_str: 342
old  15:                  '&p_str'
new  15:                  '342'

      COL1 COL2
---------- --------------
         1 2,3,4,66,342,5

SQL> /
Enter value for p_str: 66,1,8
old  15:                  '&p_str'
new  15:                  '66,1,8'

      COL1 COL2
---------- --------------
         3 4,5,2,8,99,1
         2 1
         1 2,3,4,66,342,5

SQL>