Take a look at the Win32 module (which is installed & loaded by default on most windows Perl's).

print Win32::GetOSVersion();;
Service Pack 1 6 0 6001 2 1 0 768 1

print Win32::GetOSName();;
WinVista Service Pack 1
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The interpretation of the list from Win32::GetOSVersion() is:

    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 Server 2003    2      5       2
    Windows Vista          2      6       0
    Windows Server 2008    2      6       0
    Windows 7              2      6       1
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Which should be good enough for most purposes.

i know that there are other ways to get the OS. but my toughts - which are just thoughts and nothing more - could make things easier but i also see that it could confuse other when an scalar suddenly returns an array.

As we all know, $^O always returns 'MSWin32' on windows based systems.

cygwin runs on windows, it isn't windows based :)

I am of the opinion that this sort of determination belongs exactly as it is now:   within the auspices of an appropriately-named module (presumably built-in); and not the Perl language itself. After all, a module can be defined to give you any information that you may want, in any way that you might want to have it, and yet in doing so it remains totally “a black box.” You can have it do whatever it needs to do, without muddying up either the Perl language or, much more importantly, your own code.

It is always better to have a module that gives you the answer that you want, rather than merely the means with which to figure-out that answer using your own “smarts.” This technique insulates everyone (except the maintainer of the module in question) from any Redmond brainstorm.

if ($^O eq 'MSWin32') {
    $ver = `ver`;
    $ver =~ s/\n//;
    print "Windows: $ver\n"
}
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As we all know, $^O always returns 'MSWin32' on windows based systems.

I think it'll return "MSWin64" on 64bit Windows.

So far not:

C:\test\miniball>perl -E"say $^O"
MSWin32

C:\test\miniball>perl -v

This is perl, v5.10.1 built for MSWin32-x64-multi-thread
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Ok. It looks like MSWin32 is hardcoded in source files. I also saw that several core modules check only MSWin32. So, even if this is a bug, fixing it does not seem to be worth the trouble :)