Expression sequencing query

[Wilkinson at HI-MULTICS.ARPA]

On an Intel 286/310 running Xenix 3 updt 3 I get:
  a= ((b=1),b)+((b=2),b)+((b=3),b);          RESULT a = 9
  a= (b,(b=1))+(b,(b=2))+(b,(b=3));          RESULT a = 6
          Richard Wilkinson   (Wilkinson at HI-MULTICS)