You have a list of items that are both ordered and unordered with respect to each other, and you want to sort this list to an ordered list. The definition of "ordered" is that the value of an item's  number key exists as a key in the  %ranking hash.

Sorting ordered and | ordered items that are promiscuously mingled with unordered items is tricky. I think I would approach the problem in two steps: first, extract and sort all "ordered" (per the definition above) items; second, tack all the unordered items on to the end of the sorted list.

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my @food = (
   { name => 'apple',    number =>  1 },
   { name => 'banana',   number =>  2 },
   { name => 'orange',   number =>  5 },
   { name => 'broccoli', number =>  9 },
   { name => 'grape',    number => 10 },
   { name => 'kale',     number =>  8 },
   { name => 'lemon',    number =>  5 },
   );
 ;;
 my %ranking = (
    1 => 0,
    2 => 1,
    5 => 2,
   10 => 3,
   );
 ;;
 my @ordered_then_unordered =
   sort { $ranking{$a->{number}} <=> $ranking{$b->{number}} }
   grep { exists $ranking{$_->{number}} }
   @food
   ;
 push @ordered_then_unordered,
   grep { ! exists $ranking{$_->{number}} }
   @food
   ;
 ;;
 dd \@ordered_then_unordered;
"
[
  { name => "apple", number => 1 },
  { name => "banana", number => 2 },
  { name => "orange", number => 5 },
  { name => "lemon", number => 5 },
  { name => "grape", number => 10 },
  { name => "broccoli", number => 9 },
  { name => "kale", number => 8 },
]
[download]