This command treats the variable given by varName as a listand appends each of the value arguments to that list as a separateelement, with spaces between elements.If varName doesn't exist, it is created as a list with elementsgiven by the value arguments. lappend is similar to append except that the valuesare appended as list elements rather than raw text.This command provides a relatively efficient way to build uplarge lists. For example, "lappend a $b" is muchmore efficient than "set a [concat $a [list $b]]" when $a is long.