SQL & PL/SQL

Oracle 11.1

CREATE OR REPLACE PROCEDURE foo(p_input IN clob,p_output OUT INTEGER)
IS
BEGIN
    WITH data AS (
        SELECT xmltype(p_input) xml
        FROM dual
    )
    SELECT
        length(extractValue(d.xml,'//value'))
    INTO p_output
    FROM data d;
END;
/

The incoming XML content passed into FOO may be larger than 32K so I just want to make sure Oracle can handle it but I am just not able to setup a simple test case. I googled, looked up old threads from OTN and AskTom but no matter what I do I run into either ORA-01706: user function result value was too large or ORA-06502: PL/SQL: numeric or value error: character string buffer too small

OK so extractValue returns a VARCHAR2 so it can't handle larger than 4000 but so I tried to use extract(d.dml,'//value').getclobval but that wouldn't compile with PL/SQL: ORA-22806: not an object or REF.  Clearly, I am missing some concepts here.

DECLARE
    l_clob clob;
    l_open clob := '<node><value>';
    l_close clob := '</value></node>';
    l_output INTEGER;
BEGIN
     DBMS_LOB.createtemporary(l_clob,TRUE);
     dbms_lob.writeappend(l_clob,length(l_open),l_open);
        for i in 1..10 loop
          dbms_lob.writeAppend( l_clob, 32000, rpad('*',32000,'*') );
        end loop;
     dbms_lob.writeappend(l_clob,length(l_CLOSE),l_CLOSE);

    foo(l_clob,l_output);
    dbms_output.put_line('Output='||l_output);
END;
/

Or just simply l_clob := l_open||rpad('*',32000,'*')||l_close

What am I missing? I just want to prove to myself that I can successfully pass in a XML document larger than 32K and use XMLTYPE methods to process the data in a relational format.

Thanks