use strict;
use Data::Dumper;
my @all;
my %occurances;
while (<DATA>) {
    chomp $_;
    push @all, [ split(/\|/,$_) ];
    # I should explain what is going on here
    # the -1 is going to get the last element
    # in a list.  In this case the first [-1]
    # is the last list of elements added
    # from the DATA section below with the push
    # function.  The second -1
    # is the last element of that list which
    # is the class.  The next key in the
    # occurances hash is the name_? value
    # which is extracted from the last array
    # (-1) pushed onto the @all and the first
    # element (0) of the annoymous array in
    # in that (-1) location of @all.
    $occurances{$all[-1][-1]}{$all[-1][0]}++;
                # class       # name_?
}

print Dumper(\@all);
print Dumper(\%occurances);

__DATA__
name_x|score|date|class1
name_y|score|date|class2
name_y|score|date|class2
name_a|score|date|class2
name_b|score|date|class3
name_z|score|date|class1
name_b|score|date|class3
name_x|score|date|class1
name_b|score|date|class3
name_c|score|date|class2
name_c|score|date|class3
name_c|score|date|class3