hmm... this looks really awkward:

my %list_o_num = map {
                         if(exists $list_o_num{$_})
                         {  $list_o_num{$_}++  }
                         else
                         {  $_ => 1  }
                     }
                 @list_o_num;
[download]

For one thing, you are using a hash in the same line as you declare it with my... thats bad... I think you are trying to do something like:

my %list_o_num;
$list_o_num{$_}++ for @list_o_num;

my @true_top_3 = (sort { $b <=> $a } keys %list_o_num)[0..2];

print "T3: ", join(', ',@true_top_3), "\n";
[download]

but I can't quite tell.

I would probably write that like so:

#!/usr/bin/perl -wT
use strict;

my @list_o_num = qw(9 9 9 10 9 8 7 9 6);
my %seen;
my @true_top_3 = (sort { $b <=> $a }
                       grep {!$seen{$_}++}
                            @list_o_num)[0..2];

print "T3: ", join(', ',@true_top_3), "\n";
[download]

-Blake