This doesn't concern your question (SSI is probably not enabled), but i think it is usefull to you:

CGI Scripts running on a webserver must be able to work correctly when called parallely, because they will sometime. That's why your counter will break for simultaneous access to the file. You need to lock the file using flock() and you must keep that lock active between read and write.

use Fcntl ':flock';

open my $fh, '+<' , 'visit.txt'
    or die "Error opening ..... : $!";
flock $fh , LOCK_EX;

my $counter = <$fh>;
++$counter;

seek $fh,0,0;
truncate $fh,0;

print $fh $counter

close $fh;

# ... output now
[download]

See `perldoc -f flock` as well as `perldoc -f open`.

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