My upload function looks like:

sub Upload_File{
my ($file, $mime, $description) = @_;
my $file_name   = param('filename');

my $data;

$file = UnTaint($file);

    if ($mime =~ /text/) {
            sysopen(VAULT, "$path/$file", O_RDWR | O_EXCL | O_CREAT | O_TEXT) or die "couldn't create $file for R/W: $!\n"; }
    else {
            sysopen(VAULT, "$path/$file", O_RDWR | O_EXCL | O_CREAT | O_BINARY) or die "couldn't create $file for R/W: $!\n";
    }

    my $upfh = \*VAULT;
    flock $upfh, 2;
    seek $upfh, 0, 0;
    select((select($upfh), $| = 1)[0]);
    while( sysread($file_name, $data, 8192) ) {
            syswrite($upfh, $data, 8192) or die "couldn't write $upfh: $!\n";
    }

    close $upfh; }

When I am using read and print with FastCGI upload script, files uploaded with corruptions (including simple text files), this is because perl uses buffered I/O. But when I use syswrite and sysread i.e. non-buffered I/O, as a result I get good text files, but binary files are corrupted anyway.