When I try to execute this very simple 3 line script I get Subscript out of range.
What's up?

' vbscript test of Split Function
dim a, b()
a = "this is a test"
b() = Split(a)


C:\>cscript test.vbs
Microsoft (R) Windows Script Host Version 5.1 for Windows
Copyright (C) Microsoft Corporation 1996-1999. All rights reserved.

C:\test.vbs(4, 1) Microsoft VBScript runtime error: