sub weightedprob {
    my %bias = @_;
    my ($total, %boundaries);
    
    # prepare the boundary map
    foreach ( sort { $bias{$b} <=> $bias{$a} } keys %bias ) {
        $total              += $bias{$_};
        $boundaries{$total} = $_;
    }
    
    # get a random place on the boundary map, look it up
    my $random = rand($total);
    foreach ( sort { $a <=> $b } keys %boundaries ) {
        return $boundaries{$_} if $random < $_;
    }
}

my $result = weightedprob(
  1 => 3.1,
  2 => 2.0234,
  3 => 1.7,
  4 => 1.542232,
  5 => 1.321249563,
  6 => 1.0142,
);