my $log_number = 0;
my $size = $MAXSIZE+1;
while (<>) {
    if ($size > $MAXSIZE) {
        # This will automatically close the old log file
        open(LOG, ">log-" . ++$log_number)
          or die "open: $!";
        $size = 0;
    }
    print LOG $_;
    $size += length($_);
}