The lvarpush command pushes (inserts)
string as an element in the list contained in the
variable var. The element is inserted before
position indexExpr in the list. If
index is omitted, then 0 is assumed. If
var does not exist, it is created.
If the expression indexExpr starts with the
string ``end'', then ``end'' is replaced with
the index of the last element in the list. With
``end'', the string is inserted before the last
element. If the expression starts with ``len'', then
``len'' is replaced with the length of the list.