IF (a > z) | (c < 2 * d) THEN ....
Define a, z, c, and d in the program and use the TRACE I instruction.
/****************************** REXX ********************************/
/* This program uses the TRACE instruction to show how the language */
/* processor evaluates an expression, operation by operation. */
/********************************************************************/
a = 1
z = 2
c = 3
d = 4
TRACE I
IF (a > z) | (c < 2 * d) THEN
SAY 'At least one expression was true.'
ELSE
SAY 'Neither expression was true.'
12 *-* IF (a > z) | (c < 2 * d)
>V> "1"
>V> "2"
>O> "0"
>V> "3"
>L> "2"
>V> "4"
>O> "8"
>O> "1"
>O> "1"
*-* THEN
13 *-* SAY 'At least one expression was true.'
>L> "At least one expression was true."
At least one expression was true.