sort.pl

sub sort {
  my ($self, $cb) = @_;

  return $self->new(sort @$self) unless $cb;

  my $caller = caller;
  no strict 'refs';
  my @sorted = sort {
    local (*{"$caller\::a"}, *{"$caller\::b"}) = (\$a, \$b);
    $a->$cb($b)
  } @$self;
  return $self->new(@sorted);
}