how to return a dynamic result set in Oracle function

Programmer Question

I found a string tokenizer query on the net and packaged it into the below function, which return the dynamic set of tokens. The function compiles successfully but somehow I get the error "ORA-00933: SQL command not properly ended". Can someone please help me debug this? Thank you.

CREATE OR REPLACE TYPE KEY_VALUE_TYPE is object (k varchar2(4000), v varchar2(4000));
CREATE OR REPLACE TYPE KEY_VALUE_TABLE is table of key_value_type;
CREATE OR REPLACE FUNCTION StrTokenizer
        (string IN VARCHAR2, delimiter IN VARCHAR2)
RETURN key_value_table AS
    v_ret key_value_table;
BEGIN
    SELECT
        CAST( 
            multiset(
            SELECT
                LEVEL  k, 
                SUBSTR(STRING_TO_TOKENIZE, 
                    DECODE(LEVEL, 1, 1, INSTR(STRING_TO_TOKENIZE, DELIMITER, 1, LEVEL-1)+1), 
                    INSTR(STRING_TO_TOKENIZE, DELIMITER, 1, LEVEL) 
                        - DECODE( LEVEL, 1, 1, INSTR(STRING_TO_TOKENIZE, DELIMITER, 1, LEVEL-1)+1)) v
            FROM
                (
                    SELECT
                        ':string'||':delimiter' AS STRING_TO_TOKENIZE , ':delimiter' AS DELIMITER
                    FROM
                        DUAL
                )
            CONNECT BY INSTR(STRING_TO_TOKENIZE, DELIMITER, 1, LEVEL)>0 
            ORDER BY level ASC) 
        As key_value_table)
    INTO
        v_ret
    FROM dual;
    return v_ret;
END;

select * from strtokenizer('a,b,c',',')
ORA-00933: SQL command not properly ended

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