I can't quite figure out if you want the elements in the array but not the hash, or in the hash but not the array. But here's how to get both. 
my @not_in_hash = grep {!exists $hash{$_}} @all_ids;

my %only_in_hash = %hash; #make a copy first
delete @only_in_hash{@all_ids};

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In reply to Re: stuck in a hash by Eimi Metamorphoumai
in thread stuck in a hash by Anonymous Monk

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