( MATCH )                                                       : MATCH                                                             >R >R 2DUP R> R> 2SWAP OVER + SWAP                              DO                                                                2DUP I SWAP (MATCH)                                             IF >R 2DROP R> - I SWAP - 0 SWAP 0 0 LEAVE                      THEN                                                          LOOP                                                            2DROP                                                           SWAP 0= SWAP ;                                                                                                                                                                                                                                                                                                                                                                                                                                              