ORA-14451: unsupported feature with temporary table
 *Cause:  An attempt was made to create an IOT, specify physical attributes,
          specify partition or parallel clause.
 *Action: do not do that.

ORA-14551: "cannot perform a DML operation inside a query "
 *Cause:  DML operation like insert, update, delete or select-for-update
          cannot be performed inside a query or under a PDML slave.
 *Action: Ensure that the offending DML operation is not performed or
          use an autonomous transaction to perform the DML operation within
          the query or PDML slave.

update table2 set val1 = 100 WHERE VAL1='ABC';

select function() from dual;

SELECT (SELECT some_value  INTO ...; UPDATE table2 SET ...; RETURN some_value) FROM dual

SELECT function's_return_value and, please, UPDATE some table at the same time FROM dual;