Hmmm that regex looks familiar ;-)
The problem is that you're still treating it like a network path instead of a file path. Here's a slight mod that should make it do what you want

my @NetIncludeDir = qw(C:\VENDOR\MICROSOFT\PLATFORMSDK\INCLUDE);
foreach my $file (@NetIncludeDir) {
    my($network, $path) = $file =~ m<^([\w:]+ (?:\\+ \w+) )(.*)>x;
    print "File: $file\nNetwork: $network, Path: $path\n";
}

__output__

File: C:\VENDOR\MICROSOFT\PLATFORMSDK\INCLUDE
Network: C:\VENDOR, Path: \MICROSOFT\PLATFORMSDK\INCLUDE
[download]

HTH

_________
broquaint