use strict;

my @big = qw(a b c d e f g h i);
my @small = qw(f c d g);

my @keys_wanted = @small;

foreach (@big) {
	my $found = 0;
	foreach my $already_there (@small) {

		if ($already_there eq $_) {
			$found = 1;
			last;
		}
	}
	if (!$found) {
		push (@keys_wanted, $_);
	}
}

print "@keys_wanted";