1. Fix the "content type" line.
2. Check that perl is really in /usr/bin/perl and that your program is executable. Check your web server logs.

These may fix your program if it works on the command line but not in a web browser.

Your code also seems needlessly complicated. Here's some simpler code which I adapted (okay, stole) from an answer to your frequently asked question:

# Let the Fcntl module define some constants
use Fcntl qw(:DEFAULT :flock);

# Open the counter file read/write and lock it.
# If the file hasn't been created yet, it creates one.
# Of course, the usual flock cautions apply. 
sysopen(FH, $file, O_RDWR|O_CREAT) 
    or die "Can't open $file_banner: $!\n";
flock(FH, LOCK_EX) 
    or die "Can't write-lock $file: $!\n";

# Read one line from the file. Set $num to the
# value from that line, or to zero by default.
# It's a little silly to read every line into an array
# and reference the first element if you only want 
# this one value, isn't it?
$num = <FH> || 0;

# Start at the beginning of the file
seek(FH, 0, 0)
    or die "Can't rewind $file: $!\n";
truncate(FH,0)
    or die "Can't truncate $file: $!\n";

# Print the new number to the file and close it
print FH $num+1, "\n"
    or die "Can't write to $file: $!\n";
close(FH)
    or die "Can't close $file: $!\n";
[download]

Note how the error checking is done wherever feasible so that you can get more feedback on your success/failure than that things "don't work".

buckaduck