Replacing multiple sections of a list

I need to replace odd bits of a list that are not continuous. I would have thought that I could do this with multiple calls to llListReplaceList. So that say, I could take List1, and replace elements 1-3 with List2 and put the result in List3, then replace elements 7-9 of List3 and put the result in List4, but this doesn't seem to work. List4 is just an exact copy of List3.

What's the best way to do this, please?

I don't think you can alter a list. The operation should produce a new list.

list list3 = llListReplaceList(list1, list2 , 0, 2);
list list4 = llListReplaceList(list3, <you didn't offer a source list>, 6, ;

or using fewer lists,

list replace1 = ["a", "b", "c"];
list replace2 = ["x", "y", "z"];
list1 = llListReplaceList(list1, replace1, 0, 2);
list1 = llListReplaceList(list1, replace2, 6, ;

Ah, I see where I am misunderstanding. llListReplaceList replaces the part of the first list with the whole of the second. I was trying to replace elements 1-3 of a nine element list with elements 1-3 of a second nine-element list.

Ah, in that case you could use llList2List() as the source, like this:

list LIST1 = ["A","B","C","D","E","F","G","H","I"];
list LIST2 = ["R","S","T","U","V","W","X","Y","Z"];

LIST1 = llListReplaceList(LIST1, llList2List(LIST2, 0, 2), 0, 2);
// returns: ["R","S","T","D","E","F","G","H","I"];

then,
LIST1 = llListReplaceList(LIST1, llList2List(LIST2, 6, , 6, ;
// returns: ["R","S","T","D","E","F","X","Y","Z"];

That's clever!

However, I opted for a series of one-item lists and then used llListReplaceList to replace single elements at a time. In the context, it's actually clearer than keeping all the replacement elements in a single list, as the single-element lists have meaningful names for the functions they play.