This command produces a new list from list by inserting all of the element arguments just before the index'th element of list. Each element argument will become a separate element of the new list. If index is less than or equal to zero, then the new elements are inserted at the beginning of the list. The interpretation of the index value is the same as for the command string index, supporting simple index arithmetic and indices relative to the end of the list.
set oldList {the fox jumps over the dog}
set midList [linsert $oldList 1 quick]
set newList [linsert $midList end-1 lazy]
# The old lists still exist though...
set newerList [linsert [linsert $oldList end-1 quick] 1 lazy]