#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my %data;
while (<DATA>) {
    chomp;
    my ($ln, $fn, $score) = split ' ';
    $data{$ln} = {fn => $fn, score => $score};
}
print Dumper(\%data);

# Show just last names
print "$_\n" for sort keys %data;

# Show name and score
for my $ln (sort keys %data) {
    my ($fn, $score) = @{$data{$ln}}{qw/fn score/};
    print "$ln\t$fn\t$score\n";
}

__DATA__
Lateur Bart 97
Pierce Jerrad 96
Unknown planetscape 101
Miller Katie 86