How can I upgrade alien extension on lua for windows?

I have installed Lua for windows 5.1.4-40 and it comes with alien 0.4.1.

I want to upgrade alien to 0.5.0, and couldn't figure out a way to do it.

I have luarocks installed with lua for windows, and I have tried to use it.

luaroc开发者_StackOverflowks.bat install alien

However, I got an error message saying:

*Error: Failed unpacking rockk file: C:\tmp\luarocks_....*

The reason I got the error was that I didn't run it as Administrator, although my account has admin permission. To solve this problem, I ran cygwin as administrator, and luarocks worked perfectly.