Clarify documentation of minor versions

Win32.pm

@@ -1139,8 +1139,8 @@ Currently known values for ID MAJOR MINOR and BUILD are as follows:
     Windows Server 2008 R2   2      6       1       -
     Windows 8                2      6       2       -
     Windows Server 2012      2      6       2       -
-    Windows 8.1              2      6       2       -
-    Windows Server 2012 R2   2      6       2       -
+    Windows 8.1              2      6       2/3     -
+    Windows Server 2012 R2   2      6       2/3     -
     
     Windows 10               2     10       0       -
     Windows Server 2016      2     10       0   14393
@@ -1165,6 +1165,15 @@ The version numbers for Windows 8 and Windows Server 2012 are
 identical; the PRODUCTTYPE field must be used to differentiate between
 them.
 
+The minor version number for Windows 8.1 and Windows Server 2012 R2
+depends on the running Perl version. Perl itself has been manifested
+for Windows 8.1 and Windows 10 starting from 5.24.0 (or more precisely
+from 5.23.3, if one takes development releases into account). Older
+releases of perl return the minor version as 2, while newer releases
+return it as 3. See Microsoft's L<Operating System
+Version|https://docs.microsoft.com/en-us/windows/win32/sysinfo/operating-system-version>
+documentation for more details.
+
 For modern Windows releases, the major and minor version numbers are
 identical. The PRODUCTTYPE field must be used to differentiate between
 Windows 10 and Server releases. The BUILD field is used to