my $str="17:43:33:21:23:19:27:6";

my %hash = split /:/, $str;

my $adno;

my $rand = rand 100;

my $sum = 0;
for (keys %hash) { # there is no need of sorted keys
    $adno = $hash{$_};
    last if ($sum += $_) > $rand;
}

print $adno;