lvarpush var string ?indexExpr?
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 exists, 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. If the expression starts
with len, then len is replaced with the length of
the list. Note the a value of end means insert the
string before the last element.
This command is provided by Extended Tcl.