Error printing REFCURSOR variable as OUT parameter

I am using Oracle (Oracle 11.1.0.7.0). I have created a sample stored procedure inside a package MyPackage. I was logged in as a user "DBA_USER" for creating this SP.

PROCEDURE WT_MANAGEMENT_PRODUCTIVITY 
(
cur_output Out T_CURSOR
)AS 

sqlstr VARCHAR2(5000);
 BEGIN
  Sqlstr:='select sysdate from dual';
  Open cur_output For Sqlstr;

 END WT_MANAGEMENT_PRODUCTIVITY;

I tried to call this SP using

var r ref cursor;
exec MyPackage.WT_MANAGEMENT_PRODUCTIVITY(:r);
print r;

But it throws following error in Oracle SQL Developer

Usage: VAR[IABLE] [ <variable> [ NUMBER | CHAR | CHAR (n [CHAR|BYTE]) |
VARCHAR2 (n [CHAR|BYTE]) | NCHAR | NCHAR (n) |
NVARCHAR2 (n) | CLOB | NCLOB | REFCURSOR |
BINARY_FLOAT | BINARY_DOUBLE ] ]


Error starting at line 2 in command:
exec MyPackage.WT_MANAGEMENT_PRODUCTIVITY(:r);
Error report:
ORA-06550: line 1, column 7:
PLS-00306: wrong number or types of arguments in call to 'WT_MANAGEMENT_PRODUCTIVITY'
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored
06550. 00000 -  "line %s, column %s:\n%s"
*Cause:    Usually a PL/SQL compilation error.
*Action:
r
------

EDIT1 :

T_CURSOR is type:

TYPE T_CURSOR IS REF CURSOR;

var r ref cursor;

The above is syntactically incorrect. It should be -

var r refcursor

There is not space between ref cursor, it is one word, refcursor.

For example,

SQL> create table t as select * from emp;

Table created.

SQL> var r refcursor
SQL>
SQL> begin
  2     open :r for select * from t;
  3  end;
  4  /

PL/SQL procedure successfully completed.

SQL>
SQL> delete from t;

14 rows deleted.

SQL> commit;

Commit complete.

SQL>
SQL> print r

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM
---------- ---------- --------- ---------- --------- ---------- ----------
     DEPTNO
----------
      7369 SMITH      CLERK           7902 17-DEC-80        800
        20

      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300
        30

      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500
        30


      7566 JONES      MANAGER         7839 02-APR-81       2975
        20

      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400
        30

      7698 BLAKE      MANAGER         7839 01-MAY-81       2850
        30

      7782 CLARK      MANAGER         7839 09-JUN-81       2450
        10

      7788 SCOTT      ANALYST         7566 09-DEC-82       3000
        20

      7839 KING       PRESIDENT            17-NOV-81       5000
        10

      7844 TURNER     SALESMAN        7698 08-SEP-81       1500
        30

      7876 ADAMS      CLERK           7788 12-JAN-83       1100
        20

      7900 JAMES      CLERK           7698 03-DEC-81        950
        30


      7902 FORD       ANALYST         7566 03-DEC-81       3000
        20

      7934 MILLER     CLERK           7782 23-JAN-82       1300
        10


14 rows selected.

SQL>