#!/usr/bin/perl
#!/usr/bin/env perl 

use strict;
use warnings;
use utf8;

open(GRADES, "grades.txt") or die "can't open fucking file: $!\n";
while (my $line = <GRADES>) {
    (my $student, my $grade) = split(" ", $line);
    my $grades{$student} .= $grade . " ";
}

foreach my $student (sort keys %grades){
    my $scores = 0;
    my $total = 0;
    my @grades = split(" ", $grades{$student});    
    foreach my $grade (@grades){
        my $total += $grade;
        my $scores++;
    }
    my $average = $total / $scores;
    print "$student : $grades{$student} \tMID: $average\n";
}