# prepend $log_string to @entries
my @entries = "$log_string\n";
my $logfile = 'log.txt';


##</code><code>##

open LOG, $logfile or die "Cannot open $logfile: $!";
    push @entries, scalar <LOG> for 1 .. 10;
close LOG;

open LOG, "> $logfile" or die "Cannot open $logfile: $!";
    print LOG @entries;
close LOG;