use B 'svref_2object';
use overload ();

sub bad_idea {
    my $thing = shift @_;

    local $@; # Protect against $@ stomping

    return

      # Is a real hash reference
      eval { svref_2object( $thing )->isa( 'B::HV' ) }

      # Pretends to be a hash reference
      or ( overload::Overloaded( $thing )
            and overload::Method( $thing, '%{}' ) );
}