Here you go:

my ($member,$total) = 'johndoe';
$total += $main{$_}{$member} for keys %main;
[download]

If you want to do that for each member, it would be convenient to define a %total hash with member names as keys. It could go like this:

my %total;
for my $month (keys %main) {
    $total{$_} += $main{$month}{$_} for keys %{$main{$month}};
}
[download]

I think %main could use a better name.

After Compline,
Zaxo