use List::Util qw( sum );

sub simulate_mayhem {
    my @shipsInCombat = @_;

    # Initiative levels for each ship.
    # This is a parallel array to @shipsInCombat.
    my @ship_initiatives = map {
        $_->{thruster} * 2  +  1;
    } @shipsInCombat;
    
    while ( my $total_initiative = sum @ship_initiatives ) {
    
        my $chosen_initiative = rand $total_initiative;
        my $initiative_sum = 0;
        
        # Required - can't use the loop var after the loop
        # See PBP 6.9. Non-Lexical Loop Iterators
        my $chosen_ship_number;
    
        for my $ship_number ( 0 .. $#shipsInCombat ) {
            $initiative_sum += $ship_initiatives[$ship_number];
            next if $initiative_sum <= $chosen_initiative;
            $chosen_ship_number = $ship_number;
            last;
        }
        die "Can't happen" if not defined $chosen_ship_number;
        my $chosen_ship = $shipsInCombat[$chosen_ship_number];
    
        ship_does_something($chosen_ship);
    
        # Now reduce that ship to 0, so it cannot be picked again.
        $ship_initiatives[$chosen_ship_number] = 0;
        
        # If you want, you can recalculate {thruster} on any ship
        # affected by ship_does_something(), as long as you have a
        # way of tracking the ones that had used their initiative,
        # and force it back to 0.
        ### $ship_numbers_that_used_initiative{$chosen_ship_number} = 1;
        ### recalc_thrusters(\@shipsToAct);
        ### @ship_initiatives = map {
        ###     $_->{thruster} * 2  +  1;
        ### } @shipsInCombat;
        ### ship_initiatives[$_] = 0 for keys %ship_numbers_that_used_initiative;
    }
}
# Loop exits when all ships have 0 initiative.