lvarpop var ?indexExpr? ?string?
The lvarpop command pops (deletes) the element
indexed by the expression indexExpr from the list
contained in the variable var. If index is omit-
ted, then 0 is assumed. If string, is specified,
then the deleted element is replaced by string. The
replaced or deleted element is returned. Thus
``lvarpop argv 0'' returns the first element of
argv, setting argv to contain the remainder of the
string.
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.
This command is provided by Extended Tcl.