our $ERRORSTR="";
sub new{
 ... on failure, $ERRORSTR="*KAPUT*: Monkeywrench in our NEW method";
}

sub OtherMethod{
  .. on error, $self->{ERRORSTR}="*KAPUT* I really hate that parameter you tried to pass to me";
                return -1;
}

sub errorstr{ # Both class, and Instance Method
  my ($self)=@_;
  ref $self or return $ERRORSTR; # Class call
  return defined ($self->{ERRORSTR}) ? $self->{ERRORSTR} : $ERRORSTR;
}