Here's a test program:
D = '9C34'x
Say D / You'll get "4" /
The '9C'x character is invisible in the output from "Say". It takes up no space. It is not visible when tracing an instrection such as:
C = D
OS/2 REXX displays the character as the oe ligature.
I'm using 4.1.1Beta under Linux (Debian-based)