I would actually have various tests to determine stuff.

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;
}
[download]

This way, you can check any of the possible error messages and the first time an error is checked, the file will be validated.

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We are the carpenters and bricklayers of the Information Age.

The idea is a little like C++ templates, except not quite so brain-meltingly complicated. -- TheDamian, Exegesis 6

Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.