Syntax highlighted substitution examples

This is an example that compares the two substitution styles, it is an supplement to the message it was contained in.

(r1 subst s1 by s2, s3 by s4 alt r2 subst s5 by s7) par (r3 subst s8 by empty alt r4)

(r1 (s1 := s2; s3 := s4) alt r2 (s5 := s7)) par (r3 (s8 := empty ) alt r4)