Unrelated to your problem... a loop can make your code more scalable and less error-prone (UNTESTED):

use CGI ':standard';
use warnings;
use strict;

my $total = 0;
my $div = 0;
for (1 .. 6) {
   my $g = param('g' . $_);
   if ($g ne '') {
      $total += $g;
      $div++;
   }
}

die "Error: div by 0" if $div == 0;

my $average = $total/$div;
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The code works if you add the calls around the "$average" caclulation, like:

div(); # CALL the sub named div

$average=($g1 + $g2 + $g3 + $g4 + $g5 + $g6) / $div;

letter(); #CALL the sub named letter
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Update:Here is a more concise, and idomatic version:

#!/usr/bin/perl
use strict;
use CGI qw|:standard|;

my ($count,$total);
my @gradeletter = qw| A A- B+ B B- C+ C C- D+ D |; # no F because that
+ is default;
my @gradeval = qw|92.5 89.5 87.5 82.5 79.5 76.5 72.5 69.5 66.5 62.5 |;
   
for(1..6){
  my $value = param ("g$_");
  $count++ if $value > 0;
  $total += $value;
}
$count ||=1; # Avoid divide by zero
my $average = $total / $count;
my $letter = "F"; # Default , unless a better one is found

for (0..$#gradeletter){
  if ($average > $gradeval[$_]){
     $letter = $gradeletter[$_];
     last;
  }
}

$letter = "INVALID" if $average > 100;


print ul(li(" The letter grade is $letter" )), "\n";
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I'm confused about what you are actually trying to achieve.

If the goal is to experiment with cgi scripts, or to satisfy some computer class homework assignment, this approach is fine. However, I hardly think entering 6 partial scores into a web page is the practical way to maintain grades for a class.

A spreadsheet is the obvious solution to the problem: MS Excel, GNU Gnumeric, Open Office Calc, or some other equivalent. One row for each student, one column for each landmark / assignment / test. Enter data for a column as each assignment / test is graded, and a column at the right will calculate the current total.

On a school-wide basis it would make sense to have a database, in which case you might enter the scores for all the students on assignment X at one time. But after that, no need for the user to enter the marks, the program can look them up from the database.

Thanks for all your help guys. I learned more about perl today than I thought I would but it still isn't working. I am still getting the "internal server error screen"I tried all of your advice separately and tried the code Netwallah had written but still getting the error screen even though it runs fine in the shell -konsole I am going to try some simpler scripts and try to work my way through to see if I can find the problem. thanks again for the help I appreciate any help I can get.

"Internal server error" is a web server error message. More detail will be in the web server logs - typically, this will be in /var/log/httpd/error.log .

The most common cause is that you forgot to set the script permission to 755, or did not place it in an appropriate cgi-bin directory.

     Syntactic sugar causes cancer of the semicolon.        --Alan Perlis

Thanks!! I found the error log and I almost understand what it says I assume it has something to do with the last line of the script. +Sun Mar 06 22:58:45 2011 error client 127.0.0.1 malformed header from script. Bad header=

• The letter grade is C: calc.cgi, referer: http://localhost/ I am still using the script you wrote because its very well written. I will type up my own version of it once I get this one working I just learn better if I have a working copy to start with then I take it and learn how it works. anyway I am going to mess with the last line and see if I can get it running. you have been very helpful thank you