Test MP

LISA MP+oo+oo
{
a = 1;
x = 2;
}
 P0           | P1            ;
 w[once] a 3  | r[once] r1 x  ;
 w[once] x 4  | r[once] r2 a  ;
exists (1:r1 = 4 /\ 1:r2 = 1)

C11 equivalent: c11-prop-src/mp+o-o+o-o.litmus