perl -we 'sub b { my $a; *b = \&c; b() } sub c { die "here" } b()'

##</code><code>##

  package NVC::DB::User;
  sub bless {
    my $self = shift;
    my $config = $self->config;

    # do this only once, on first call
    no warnings qw/ redefine /;
    if ($config->extend_user('type 1')) {
      *bless = \&bless_type1;
    } elsif ($config->extend_user('type 2')) {
      *bless = \*bless_type2;
    } else {
      *bless = \&bless_simple;
    }
    return $self->bless(@_);
  }