foo(X):- R is random(3)+1, arg(R,v(bar,baz,boo),X).


?- forall(between(1,1000,_),
      (foo(X),flag(X,V,V+1))),
  flag(bar,BAR,0), flag(baz,BAZ,0), flag(boo,BOO,0).


% cumulative version

?- forall(between(1,1000,_),
      (foo(X),flag(X,V,V+1))),
  flag(bar,BAR,BAR), flag(baz,BAZ,BAZ), flag(boo,BOO,BOO).