o<g843> sub

(debug, in g843 x=#<x>  y=#<y>  z=#<z>  p=#<p>  q=#<q>)

O100 if [exists[#<p>] NE 1.]
     (debug, the P word was not set)
O100 endif

; signal success be returning a value > 0:
o<g843> endsub [1]

m2

