sub roll {
    my ($max) = @_;
    return 1 + int rand $max;
}

sub sum {
    my $sum = 0;
    $sum += $_ for @_;
    return $sum;
}

my @dice;

ROLL: for (1..4) {
    push @dice, roll 6;
    pop @dice and redo ROLL if $dice[-1] == 1; 
}

# Discard lowest
@dice = sort { $a <=> $b } @dice;
unshift @dice;

my $sum = sum @dice;