package MyIO;

sub isa
{
  my $self = shift;
  my $type = shift;

  return 1 if $type eq 'IO::Handle';

  return $self->SUPER::isa($type);
}

##</code><code>##

package MyNotIO;

use base 'IO::Handle';

sub isa
{
  my $self = shift;
  my $type = shift;

  return 0 if $type eq 'IO::Handle';

  return $self->SUPER::isa($type);
}

##</code><code>##

package UNIVERSAL;

sub safe_isa
{
  my $obj = shift;
  return unless defined $obj and ref $obj;

  $obj->isa(@_);
}