BLOB to CLOB using APEX_WEB_SERVICE

APEX_WEB_SERVICE.BLOB2CLOBBASE64 (
     p_blob IN BLOB)
RETURN CLOB;

declare
    l_clob CLOB;
    l_blob BLOB;
begin
    SELECT BLOB_CONTENT
      INTO l_BLOB
      FROM APEX_APPLICATION_FILES
      WHERE name = :P1_FILE_NAME;
 
    l_CLOB := apex_web_service.blob2clobbase64(l_BLOB);
end;