SUB BETWEEN$(TXT$, LHS$, RHS$, AFTER)
	LET LHS = POS(TXT$, LHS$, AFTER)
	IF LHS = 0 THEN
		'LHS$ NOT FOUND IN TXT$. RETURN EMPTY STRING
		RETURN ""
		EXIT SUB
	END IF
	LET RHS = POS(TXT$, RHS$, LHS + LEN(LHS$))
	IF RHS = 0 THEN
		'NO RHS$ FOUND IMMEDIATELY AFTER LHS$ IN TXT$. RETURN EMPTY STRING.
		RETURN ""
		EXIT SUB
	END IF
	RETURN SEG$(TXT$, LHS + LEN(LHS$), RHS-1)
END SUB

DECLARE SUB REPLACE$(INTHIS$, FINDTHIS$, WITHTHIS$)
	LET T = POS(INTHIS$, FINDTHIS$)
	RETURN INTHIS$
	IF T <> 0 THEN
		MID$(INTHIS$, T, LEN(FINDTHIS$)) = WITHTHIS$
		RETURN INTHIS$
	END IF
END SUB

LET STORY$ = ""
LET STORYLINE$ = ""
WHILE TRUE
	LINE INPUT "Enter line of story (empty line to stop)"; STORYLINE$
	IF STORYLINE$ = "" THEN
		EXIT WHILE
	END IF
	STORY$ = STORY$ + " " + STORYLINE$
END WHILE

WHILE TRUE
	LET TXT$ = ""
	LET KEY$ = BETWEEN$(STORY$, "<", ">", 0)
	IF KEY$ <> "" THEN
		PRINT "PLEASE ENTER A " + KEY$;
		LINE INPUT TXT$
		LET SRCH$ = "<" + KEY$ + ">"
		STORY$ = REPLACE$(STORY$, SRCH$, TXT$)
	ELSE
		EXIT WHILE
	END IF
END WHILE

PRINT STORY$