Insert Into()

[#1]

Hi,

I have a number of lists, of varying length, and I'd like to combine all the items in the lists into one list. 

For example: 

list1 = {"a", "b", "c"};
list2 = {"d", "e"};
list3 = {"f", "g", "h", "i"};
.... the number of lists ranges from 7 to 10.

Want to create

list = {"a", "b", "c", "d", "e"};

I have been creating the final list

Insert Into(list1, list2);
Insert Into(list1, list3);
.... and so on. 
(I don't mind the list items are added to list1)

Is there a more efficient way of doing this? Insert Into() doesn't seem to take more than 1 add-on parameter. 

Thank you.

[#2]

That is the best you can do if you are happy to update list1.

If you want a new list, leaving the old lists unchanged, the best choice between these

        lnew = l1 || l2 || l3;
// vs
        lnew = insert( l1, l2 ); lnew = insert( lnew, l3 );

depends on the length of the lists, though || eventually pulls ahead in the graph below.

All three are within a factor of 2 of the same speed. I like insertInto() because it avoids copying list1. I like the || concatenation operator because it is clear what it is doing.

InsertInto wins if you don't mind that it does what its name says.