open FH1, "what.txt" or die $!;
    open FH2, "what1.txt" or die $!;

    my($buf1, $buf2, $total);
    while (read(FH1, $buf1, 1) && read(FH2, $buf2, 1)) {
        $total .= $buf1 . $buf2;
    }

    close FH1;
    close FH2;