# doesn't reference anything outside the scope of the subroutine scope

sub not_a_closure {
  my $i;
  $i++;
  return $i
}

# references a package variable, not a lexical variable

our $global;
sub also_not_a_closure {
  $global++;
  return $global;
}

# a closure -- references a lexical outside the scope

my $lexical;
sub a_closure {
  $lexical++;
  return $lexical;
}

# anonymous closure generator -- references a new variable each time

sub closure_generator {
  my $fresh_lexical;
  return sub {
    $fresh_lexical++;
    return $fresh_lexical;
  }
}