my %lookup = (
   1 => {
      90 => 'Win ME',
      10 => 'Win 98',
   },
   2 => {
      3 => 'Win NT 3.51',
      4 => 'Win NT 4.0',
      5 => {
         0 => 'Win 2k',
         1 => 'Win XP',
      },
   },
);

my $os = $lookup{$id}->{$minor};
$os    = $os->{$major} if $minor == 5;
$os  ||= 'Unknown Win32s flavor';

print "$os, $major.$minor\n";