my $OS                  = $^O;
if ($OS =~ m/win32/i)  {
    eval "use Win32::File";
    eval "use Win32::FileSecurity";
}
if ($OS =~ /darwin/) {
    do something else
}
if ($OS =~ m/win32/i) {
    my $attrib;
    Win32::File::GetAttributes($http_rec_localdir, $attrib);
    if ($attrib & (Win32::File::SYSTEM | Win32::File::HIDDEN)) {
        &error_dialog( "Destination Directory",
               "Destination directory is not writable." );
        return;
    }
}