how can i get Oses NT 4 and Vista when they have the same minor and id

By looking at the major part of the version.

use constant VER_PLATFORM_WIN32_WINDOWS => 1;  # Win9x line
use constant VER_PLATFORM_WIN32_NT      => 2;  # WinNT line

use constant VER_NT_WORKSTATION => 1;

my %oses = (
    '9x 4.0 ???'  => '95',
    '9x 4.10 ???' => '98 or 98 SE',
    '9x 4.90 ???' => 'Me',
    'NT 3.51 ???' => 'NT3.51',
    'NT 4.? ???'  => 'NT4',
    'NT 5.0 WS'   => '2000',
    'NT 5.1 WS'   => 'XP',
    'NT 5.2 ???'  => 'XP Professional x64 Edition, '
                    .'Server 2003, '
                    .'Server 2003 R2 or '
                    .'Home Server',
    'NT 6.0 WS'   => 'Vista',
    'NT 6.0 !WS'  => 'Server 2008',
    'NT 6.1 WS'   => '7',
    'NT 6.1 !WS'  => 'Server 2008 R2',
);

my ($id, $major, $minor, $prod_type) =
    ( Win32::GetOSVersion() )[4,1,2,8];

my $id_str = join(' ',
    $id == VER_PLATFORM_WIN32_NT ? 'NT' : '9x',
    "$major.$minor",
    $prod_type == VER_NT_WORKSTATION ? 'WS' : '!WS' ],
);

my $os = $oses{$id_str};
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(Replace the "???" with the missing information.)

See Getting the System Version. OSVERSIONINFOEX is also interesting.