You're question is rather vague.. From the terminology you used in the question I'm guessing you're in a windows environment, wanting to know what type of windows OS a machine is, what service packs it has, etc..

There are many available options, but a general question deserves a general answer. Look into WMI (Windows Management Instrumentation) - it can be accessed using Win32::OLE. As part of SDK/administration packs from Microsoft there are examples of how to tap WMI from various scripting languages.(including perl)