# Parallel arrays: Sort our data by age
my @indices = sort { $age[$a] <=> $age[$b] }  0 .. $#first_name;
@first_name = @first_name[@indices];
@last_name  = @last_name[@indices];
@age        = @age[@indices];

print "Using parallel arrays, sorted by age\n";
for my $i (0 .. $#first_name) {
    print "$first_name[$i] $last_name[$i] $age[$i]\n";
}