That piece of doc expains dosish platforms, so it is closely related to Win32::GetOSVersion function.
perldoc Win32 contains an answer to your question:
[CORE] Returns the array (STRING, MAJOR, MINOR, BUILD, ID), where
the elements are, respectively: An arbitrary descriptive string, t
major version number of the operating system, the minor version
number, the build number, and a digit indicating the actual
operating system. For the ID, the values are 0 for Win32s, 1 for
Windows 9X and 2 for Windows NT/2000/XP. In scalar context it
returns just the ID.
Currently known values for ID MAJOR and MINOR are as follows:
OS ID MAJOR MINOR
Win32s 0 - -
Windows 95 1 4 0
Windows 98 1 4 10
Windows Me 1 4 90
Windows NT 3.51 2 3 51
Windows NT 4 2 4 0
Windows 2000 2 5 0
Windows XP 2 5 1
Windows .NET Server 2 5 1
Unfortunately as of June 2002 there is no way to distinguish betwe
.NET servers and XP servers without using additional modules.
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