Updated sort to numeric!

sub grade{ 
    my (%h, %i); 
    @h{ ('A' .. 'I')[0..$#_] } = @_; 
    @i{ values %h } = keys %h; 
    @i{ sort{ $b <=> $a } keys %i }; 
}
my @n=(5, 100, 2, 8, 40);
print grade @n;
B E D A C
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