Date Parameter in Sql scripts help needed

I have an sql script something like

select * from emp where hire_date
>>TO_DATE(&&PARAM_DATE,'DD-MON-YYYY')
PARAM_DATE is the parameter i pass to the sql script.

I call the sql script from SQLPLUS. But when i execute it, i get "invalid column name". It becomes hire_date >> 1-JAN-2001

How do i insert the escape characters? Received on Mon Dec 24 2001 - 00:13:01 CST