until ( $cash > $goal or $date == 31 ) {

    # update prices
    foreach my $stock ( @ticker{@stock_names} ) {
        $$stock{price} += generate_random($$stock{volitility});
        $$stock{price} = 0 if $$stock{price} < 1;
    }

    # liquidate holdings if price hits 0
    foreach my $stock ( @stock_names ) {
        $portfolio{$stock} = 0 if $ticker{$stock}{price} == 0
    }

    $date++;
    print qq|Last Day!! better sell your stock| if $date == 30;

    while (1) {
        notify_user(daily_report(\%portfolio, \%ticker, $cash, $date));
        my $transaction =
            query_user( q|Would you like to (B)uy or (S)ell |,
                        q|or are you (D)one? | );

        if ($transaction =~/^s/i) {
            $cash += sell(\%portfolio, \%ticker);

        } elsif ($transaction =~/^b/i) {
            $cash = buy(\%portfolio, \%ticker, $cash);

        } elsif ( $transaction =~ /^d/i ) {
            last;

        } elsif ( $transaction =~ /^q/i ) {
            exit;
        }
    }
}