You can add replace or remove prefixes with this
Code:
(DEFUN C:RLP ()
(PROMPT "\n*REPLACE LAYER PREFIX* ")
(SETQ LTSRL 1)
(SETQ LPRE (GETSTRING "\nEnter existing layer prefix<none>: "))
(SETQ NLPRE (GETSTRING "\nEnter new layer prefix<none>: "))
(SETQ LP 1)
(WHILE LP
(SETQ LTS (TBLNEXT "LAYER" LTSRL))
(SETQ LTSRL NIL)
(IF (/= LTS NIL)
(PROGN
(SETQ LTST (CDR (ASSOC 2 LTS)))
(SETQ LTSTL (STRLEN LTST))
(SETQ CP 1)
(SETQ LP2 1)
(WHILE LP2
(SETQ LS (SUBSTR LTST 1 CP))
(SETQ CP (+ CP 1))
(IF (AND (= LPRE "") (/= LTST "0"))
(PROGN
(SETQ NLN (STRCAT NLPRE LTST))
(COMMAND "RENAME" "LA" LTST NLN)
(SETQ LP2 NIL)
));END PROGN/IF LS
(IF (AND (= LS LPRE) (/= LTST "0"))
(PROGN
(SETQ NLN (STRCAT NLPRE (SUBSTR LTST CP)))
(COMMAND "RENAME" "LA" LTST NLN)
(SETQ LP2 NIL)
));END PROGN/IF LS
(IF (> CP LTSTL) (SETQ LP2 NIL))
);END LP2
));END PROGN/IF LTS
(IF (= LTS NIL) (SETQ LP NIL))
);END LP
(PRINC)
);END RLP