#!/usr/bin/perl -w

use strict;

my %grades;

while (<DATA>) {
     chomp;
     my($student,$grade) = split (" ",$_);
     $grades{$student} .= $grade . " ";
     #$grades{$student} = $grade;
     print "\$grades{$student} is $grades{$student}\n";
      
}

for (sort keys %grades) {
    my $scores = 0;
    my $total  = 0; 
    my @grades = split(" ", $grades{$_});
    for (@grades) {
       $total += $_;
       $scores++;
    }
    my $average = $total / $scores;
    print "$_: $grades{$_}\tAverage: $average\n";
}

__END__
lee  90
lee  100
kim  90
kim  90




./././perl.score
$grades{lee} is 90 
$grades{lee} is 90 100 
$grades{kim} is 90 
$grades{kim} is 90 90 
kim: 90 90      Average: 90
lee: 90 100     Average: 95


so 
$grades{$student} .= $grade . " "; is more like

$grades