Why is my script adding to both lists?

[bh]

You are setting both variables to the same (empty) list in the first instruction.

I copied a list to another variable, and then when I change the copy, it changes the original too!

Short answer: You didn't copy the list to the variable, you gave the same list another name. [The pictures below are a lie. See below the divider -------- for the full story.] Here's what it looks like: [untitled%20script%20pic] [Stage] The list is made of pairs, each of which points to one list item (left half) and to another pair (right half). The right half of the last pair is a special empty-list object. [untitled%20script%20pic%20(2)] The variable FOO points to the list, and the S…