The problem is that param("Game") does not return one of the keys you initialize your hash %game with. Consider

use strict;
use warnings;

#this is better syntax for creating a hash
my %game_count = ("Great" => 0, "Boring" => 0, "None" => 0);
my $game = "Great";
# no warning
$game_count{$game} = $game_count{$game} + 1;
[download]

but

use strict;
use warnings;

#this is better syntax for creating a hash
my %game_count = ("Great" => 0, "Boring" => 0, "None" => 0);
my $game = "Something";
# this yields the warning
$game_count{$game} = $game_count{$game} + 1;
[download]

Furthermore you can replace $game_count{$game} = $game_count{$game} + 1; with $game_count{$game}++;