Does anybody know what is the ID column in the following table and where it comes from? The table is taken from perlport manpage:

 OS            $^O      $Config{archname}   ID    Version
--------------------------------------------------------
MS-DOS        dos        ?
PC-DOS        dos        ?
OS/2          os2        ?
Windows 3.1   ?          ?                 0      3 01
Windows 95    MSWin32    MSWin32-x86       1      4 00
Windows 98    MSWin32    MSWin32-x86       1      4 10
Windows ME    MSWin32    MSWin32-x86       1      ?
Windows NT    MSWin32    MSWin32-x86       2      4 xx
Windows NT    MSWin32    MSWin32-ALPHA     2      4 xx
Windows NT    MSWin32    MSWin32-ppc       2      4 xx
Windows 2000  MSWin32    MSWin32-x86       2      5 xx
Windows XP    MSWin32    MSWin32-x86       2      ?
Windows CE    MSWin32    ?                 3
Cygwin        cygwin     ?
[download]

I found no clue in either the Config manpage or perlport one. I know i should rely on other modules to know the exact OS under Windows, but i'd like to use that ID column if possible.

$|=$_="1g2i1u1l2i4e2n0k",map{print"\7",chop;select$,,$,,$,,$_/7}m{..}g