@array = 1..100;;
@hash{ 0 .. 99 } = @array;;
cmpthese -1,{
    a=>q[my$t=0; $t+=$_ for @array;],
    b=>q[my$t=0; $t+=$hash{$_} for keys %hash;] 
};;
      Rate    b    a
b  35255/s   -- -66%
a 103177/s 193%   --