For a last-century example of actual pass-by-reference, assign-by-copy, the PL/I program

  foo: proc options(main);
    dcl sysprint print;
    dcl a(3) fixed bin(31) init(1,2,3);
    put skip data (a);
    call bar(a);
    put skip data (a);
  
  bar: proc(x);
    dcl x(3) fixed bin(31);
    dcl b(3) fixed bin(31) init(3,2,1);
    x = b;
    b(1) = 42;
    x(2) = 42;
    put skip data (b);
    put skip data (x);
  end bar;
  
  end foo;

outputs

  A(1)=   1   A(2)=   2   A(3)=   3 ;
  B(1)=  42   B(2)=   2   B(3)=   1 ;
  X(1)=   3   X(2)=  42   X(3)=   1 ;
  A(1)=   3   A(2)=  42   A(3)=   1 ;

demonstrating that X refers to A in BAR and assigning B to X copies B into X (= A).