use strict;

my %odds = ( 1 => 80, 2 => 10, 3 => 10 );

for my $i (1..25) {
    print "$i: ", &go, "\n";
}

sub go {
    my $i = int(rand(100) + 1);

    foreach my $k (keys %odds) {
        $i -= $odds{$k};
        return $k if $i <= 0;
    }

    return undef;
}