my %bias = (
   1 => 3.1,
   2 => 2.0234,
   3 => 1.7,
   4 => 1.542232,
   5 => 1.321249563,
   6 => 1.0142,
 );
my $sum = 0;
while( my($k,$v) = each %bias ){
    $rand = $k if rand($sum+=$v) < $v;
}