jcparkyn

  for x in arr (something ())
           \                 /-- function call

  for x in arr (something ())
               \            /-- loop body

  for x in arr do set z += x;
  for x in arr do something x;

  x = [1, [2]];
  var y = x;
  set y.[0] = 3; // clones the outer array, keeps a reference to inner array
  set y.[1].[0] = 4; // clones the inner array here. Outer array is now exclusive so it doesn't need another clone.

  var z = x;
  set z.[1].[0] = 4; // clones both arrays at once

    x = 1; // declares x as immutable
    var y = 2; // declares y as mutable