RE: substr bif question

You will need to bifs.

Work = %Subst(string: 1: 3);
If %Len(%TrimR(string)) > 3 and (work = 'A' or work = 'B' ...);
If you don't include the test for the length of the field, you
will get string 'A' as falling into your code.
This may or may not be acceptable. In this case I would not
use multiple %Subst() in the if statement due to making the
routine faster.

Not sure I understand this person's language, but I can say that all of the
solutions I have seen here will get you into trouble if STRING is a
varying-length field with a current length of less than 3 bytes. And you
were correct in surmising that stating %SUBST three times might be less
efficient than one move to a 3-byte field.

If I were charged with this, I would create a 3-byte, no-varying-length
field (myString), and EVAL myString = string.

Then a simple:
IF (myString = 'A' or myString = 'B' or myString = 'C') ;
// do stuff
Else ;
// do other stuff
EndIF ;

Would fill the bill, and operate efficiently with no need for length checks.
Note that you do not need to specify trailing blanks in a string comparison.
'A' is equal to 'A ' all day long from that perspective. One is more
readable (at least that's my opinion), and the other has a tendency to make
one stop and count unnecessarily.

Regards,
Dennis

Dennis Lovelady
--
"For a moment, nothing happened. Then, after a second or so, nothing
continued to happen."
-- The Hitchhiker's Guide to the Galaxy