if ($email->is_duplicate) { ... }
if ($email->is_profane) { ... }
# etc ...

package MyEmail;

sub is_duplicate
{
    my $self = shift;

    $self->validate unless $self->is_validated;

    return $self->{is_duplicate};
}

# all the others are the same

sub validate
{
    my $self = shift;

    # set some attributes

    $self->{is_validated} = 1;
}