simple xml parser

CREATE OR REPLACE FUNCTION dwfacts.parse_xml(p_string IN VARCHAR2
,p_node IN VARCHAR2
)
RETURN VARCHAR2
AS
v_data VARCHAR2(4000);
v_node VARCHAR2(4000);
v_upper_str VARCHAR2(4000);
v_startnode VARCHAR2(4000);
v_endnode VARCHAR2(4000);
v_startnodelength NUMBER;
BEGIN
v_node := UPPER(p_node);
v_upper_str := UPPER(p_string);
v_startnode := '<'||v_node||'>';
v_endnode := '';
v_startnodelength := LENGTH(v_startnode);

v_data := SUBSTR(p_string,INSTR(v_upper_str,v_startnode)+v_startnodelength);
v_data := SUBSTR(v_data,1,INSTR(UPPER(v_data),v_endnode)-1);
RETURN(TRIM(v_data));
END;