1 sub check_required_items { 
2 	my $who = shift;
3 	my $items = shift;
4 
5 	my %whose_items = map { $_, 1 } @$items;
6 
7 	my @required = qw(preserver sunscreen water_bottle jacket);
8 	my @missing = ( );
9 
10 	for my $item (@required) {
11 		unless ( $whose_items{$item} ) { # not found in list?
12 		print "$who is missing $item.\n";
13 		push @missing, $item; }
14 	}
15 
16 	if (@missing) {
17 		print "Adding @missing to @$items for $who.\n"; 
18 		push @$items, @missing;
19 	} 
20 }