sub mk_less_than_filter {
  my $limit = shift;
  return sub { my $elt = shift; return $elt < $limit; };
}

sub find_less_than {
  my $limit = shift;
  my $vals = shift;
  my $filter = mk_less_than_filter($limit);
  return grep {$filter->($_)} @$vals;
}

print join(", ", find_less_than(4, [1, 2, 7, 10, 3, 8])), "\n";


# Prints 1, 2, 3