Basic Perl Scripting
Exercise 2
To be handed in: Thursday 11th of October

In this exercise we will process the contents of a file. Carefully
read the average example (page 17 in the 3.edition, page 10 in the
2. edition of Programming Perl, Wall). It is given below. Try to
understand what is going on in the script.

Grade example: 

Suppose you had a set of scores for each member of a class you are
teaching. You'd like a combined list of all the grades for each
student, plus their average score. You have a text file (imaginatively
named grades) that looks like this:

Noel 25
Ben 76
Clementine 49
Norm 66
Chris 92
Doug 42
Carol 25
Ben 12
Clementine 0
Norm 66
...

You can use the following script to gather all their scores together,
determine each student's average, and print them all out in
alphabetical order. This program assumes, rather naively, that you
don't have two Carols in your class. That is, if there is a second
entry for Carol, the program will assume it's just another score for
the first Carol (not to be confused with the first Noel).  By the way,
the line numbers are not part of the program, any other resemblances
to BASIC notwithstanding.

1 #!/usr/bin/perl
2
3 open(GRADES, "grades") or die "Can't open grades: $!\n";
4 while ($line = <GRADES>) {
5 ($student, $grade) = split(" ", $line);
6 $grades{$student} .= $grade . " ";
7 }
8
9 foreach $student (sort keys %grades) {
10 $scores = 0;
11 $total = 0;
12 @grades = split(" ", $grades{$student});
13 foreach $grade (@grades) {
14 $total += $grade;
15 $scores++;
16 }
17 $average = $total / $scores;
18 print "$student: $grades{$student}\tAverage: $average\n";
19 }

Now before your eyes cross permanently, we'd better point out that
this example demonstrates a lot of what we've covered so far, plus
quite a bit more .... .
 
Your Exercise: 

Use the following list and write a program close to the above example,
which gives you the average grade for females and for males. The below
list will be send out electronically also, to facilitate processing.

Name     Grade   Gender
Johannes 25      male
Kathrin  26      female
Polina   44      female
Kai      20      male 
Anna     33      female 
Valentin 40      male 
Peter    23      male 
Mathias  30      male
Barbara  34      female

Hand in your script and the output. 

Good luck!