grep EXPR, LIST

Evaluates the BLOCK or EXPR for each element of LIST (locally setting $_ to each element) and returns the list value consisting of those elements for which the expression evaluated to true.

So, in this case, grep takes a list and returns a list.

my @list = (1, 2, 3, 4, 5);
my @result = grep $_ > 2, @list;
print "@result";
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3 4 5
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You could probably get away with something like

if (exists $item_lookup{$name}){
  print qq{$name has $item_lookup{$name}};
else{
  print qq{$name is missing $item_lookup{$name};
}
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in your for loop.