I took it for granted that Brian changed BOTH the index expression AND the select statement. Obviously he did not, I just tried it myself, and it worked as expected, with full optimization.

SET ANSI OFF
SET EXACT ON
CLEAR
* Turn rushmore reporting on
SYS(3054,2)
* Create a test cursor
CREATE CURSOR test (field C(10))
INDEX on field TAG field
INDEX on PADR(field,5) TAG field_t
* Put some data in the cursor
FOR i = 1 TO 10000
 INSERT INTO test VALUES (SYS(2015))
ENDFOR

* Determine the last value
cValue = LEFT(test.field,LEN(ALLTRIM(test.field))-1)
* Try the untrimmed index
?"This one works"
?"---------------------------------"
SELECT * FROM test WHERE field = cValue INTO CURSOR index
* Try the trimmed index
?
?"This one does not work"
?"---------------------------------"
SELECT * FROM test WHERE PADR(field,5) = cValue INTO CURSOR noindex

>I think VFP compares the KEY of index and if thay doesn't match VFP doesn't use this tag for Optimization.