#!/usr/bin/env perl
use 5.010;
use strict;
use warnings;
use Data::Dump qw/pp dd/;

my %vote = ( alligator => 100, bear => 90, cat => 80, jellyfish => 10 );
my $N =0;
$N += $_ for values %vote;
say "Vote";
show(\%vote, 1);

# --- invert by exponentiation
for my $C ( 0.9, 0.95, 0.96, 0.97, 0.98, 0.99) {
    my $N4=0;
    my %vote4 = map {
        my $v4 = $C ** $vote{$_};
        $N4 += $v4;
        $_ => $v4;
    } keys %vote;

    my %dist4;
    my $e=5;
    $dist4{pick($N4,\%vote4)}++ for 1..10**$e;
    say "C=$C";
    show( \%dist4, -1);
}

sub show { # show counts and percentages
    my $href = shift;
    my $dir = shift; # sort direction 1=ascending, -1=descending
    my $tot=0;
    $tot += $_ for values %$href;
    for my $k (sort {$dir * ($a cmp $b)} keys %$href) {
        printf "%s => %5d (%5.2f%%)  ", 
               $k, $href->{$k}, 100*($href->{$k}/$tot);
    }
    say '';
}

sub pick {
    my ($N,$h_vote)=@_;
    my @deb;
    my $r   =rand($N);
    push @deb,$r;
    scalar keys %$h_vote;                 # reset each
    while ( my ($k,$v) = each %$h_vote) {
        $r -= $v;
        push @deb,[$r,$k,$v];
        return $k if $r <=0;
    }
    die "ERROR", pp \@deb;
}