So I'm just learning perl so I hope you don't mind me posting already, or with simple questions.

I'm trying to write a simple program that creates a list of Students' grades and average grades on assignments from a text file. I can get the first part to work and get the proper calculations for the second. However when I try to sort the arrau then my output doubles and have of it comes with an error

Use of uninitialized value in print at ./hw3.pl line 30, <STDIN> line 9.

here is the code:

#!/usr/bin/perl -w

%totals = (), %hwsum = (), %hwtimes = ();
while ($line = <STDIN>)
{
    chomp $line;
    ($student, $assign, $grade) = split /:/, $line;
    $totals{$student} += $grade;
    $hwsum{$assign} += $grade;
    $hwtimes{$assign} += 1;
    $average{$assign} = $hwsum{$assign} / $hwtimes{$assign};
}

@all = keys %totals;
@all = sort {$totals{$b} <=> $totals{$a}} @all;
@hwall = keys %average;
@hwall = sort (%average);

print "*** STUDENT TOTALS ***\n";

  foreach $st (@all)
{
    print $st, ":  ", $totals{$st}, "\n";
}

print "*** HOMEWORK AVG ***\n";

foreach $phw (@hwall)
{
    print $phw, ":  ", $average{$phw}, "\n";
}
[download]

and here is the output

*** STUDENT TOTALS ***
cindy:  24
david:  19
alice:  15
bob:  11
*** HOMEWORK AVG ***
Use of uninitialized value in print at ./hw3.pl line 30, <STDIN> line 
+9.
7:
Use of uninitialized value in print at ./hw3.pl line 30, <STDIN> line 
+9.
8:
Use of uninitialized value in print at ./hw3.pl line 30, <STDIN> line 
+9.
8:
hw1:  8
hw2:  8
hw3:  7
[download]

Thanks for any help

--Jeeves

20050413 Janitored by Corion: Added code tags