Change object in place rather than creating new copy

Co-authored-by: Danny Glin <dlglin@ucalgary.ca>

Author: lahvak

OpenProblemLibrary/AlfredUniv/anton8e/chapter1/1.5/prob9.pg

@@ -44,7 +44,8 @@ TEXT(beginproblem());
 
 $ans1 = Formula("1/sqrt(x**2 + 1)")->reduce;
 $ans2 = Formula("sqrt(1-1/x**2)")->reduce;
-$ans2 = $ans2->with(limits=>[1.1, 10], test_at=>[[-2],[-3]]);
+$ans2->{limits}=[1.1, 10];
+$ans2->{test_at}=[[-2],[-3]];
 
 Context()->texStrings;
 BEGIN_TEXT