Debugging a "compiled" REXX program

Sometimes it's neccessary to debug a REXX program from which the source 
code is not available. 
In this case issue 

 
  set rxtrace=on

in an OS/2 window and call the program from this window. 

(see also Catching debug output, Get the source code of a "compiled" REXX 
program, and Special environment variables for REXX programs)