my @required_items = qw( apple orange pear );

foreach my $collection (@collections) {
  my %seen = ();
  foreach my $item ( ... ) { # however you get the items out of $collection
    $seen{$item} = undef;
  }
  foreach my $item (@required_items) {
    if ( ! exists($seen{$item}) ) {
      # do something to insert it
    }
  }
}