Finding parameter names for binding stored procedure parameters
I did a little bit more research and found the answer to the problem.  

Even though the first parameter for DBMS_OUTPUT.PUT_LINE is listed as item in the 10g documentation for DBMS_OUTPUT. The actual name for the parameter is A. You need to bind the name using DBMS_OUTPUT.PUT_LINE(A =&gt; 'random text').

The actual parameter names for stored procedures can be discovered using the following query:  

SELECT 
    argument_name, 
    in_out, 
    data_type 
FROM 
    all_arguments 
WHERE 
    owner = 'SYS' --owner for said procedure
    AND package_name = 'DBMS_OUTPUT' --if procedure is in a package that name, null otherwise
    AND object_name = 'PUT_LINE' --procedure name


The values SYS, DBMS_OUTPUT, and PUT_LINE can be replaced with the values of the the stored procedure that you would like to look up.