# ./foo.pl 
use strict;
use warnings;

use lib ('/path_to_Word_pm');
use Word;

my $word = Word->new();
$word->set('apple','it');

# ./Word.pm
package Word;

use strict;
use warnings;
use base 'WordExposed::Languages';

sub new {
    my $class = shift;
    my $self  = {};
    bless($self, $class);
    return $self;
}
sub set {
    my $self = shift();
    my $english = shift();
    my $language = shift();
    $self->{english} = $english;
    $self->{language} = $language;
    $self->_translate();
}
1;

# ./WordExposed/Languages.pm
package WordExposed::Languages;

use WordExposed::LanguagesPrivate::French;
use WordExposed::LanguagesPrivate::Italian;

sub _translate {
    my $self = shift();
    if ($self->{language} eq 'fr') {
        $self->_traduction();
    } elsif ($self->{language} eq 'it') {
        $self->_traduzione();
    }
}

1;

# ./WordExposed/LanguagesPrivate/French.pm
package WordExposed::LanguagesPrivate::French;

our @ISA       = qw(Exporter);
our @EXPORT    = qw( _traducion );
our @EXPORT_OK = qw();

sub _traducion {
    my $self = shift();
    warn 'pomme' if ($self->{english} eq 'apple');
}
1;

# ./WordExposed/LanguagesPrivate/Italian.pm
package WordExposed::LanguagesPrivate::Italian;

our @ISA       = qw(Exporter);
our @EXPORT    = qw( _traduzione );
our @EXPORT_OK = qw();

sub _traduzione {
    my $self = shift();
    warn 'mela' if ($self->{english} eq 'apple');
}
1;
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If I don't use Class:Struct it works the way I want (as in the following code). Here ./Word.pm only "knows" about ./WordExposed/Languages.pm. I cannot get something similar with structures.

Ah, I see. Sorry, I haven't used Class::Struct, so I can hardly comment. Some confrater please take over.

Update: A look at the documentation shows this rather serious limitation:

The class created by "struct" must not be a subclass of another class other than "UNIVERSAL".

In other words: The simple (and standard) solution I proposed won't work with Class::Struct

You could try this: Make an extra class, say Word::Struct that contains the Class::Struct-related stuff. Then, in class Word, inherit from both Word::Struct and WordExposed::Languages.

Meanwhile, your best course may be be to work out the different behavior of a "standard" class and a Class::Struct based one in a small, independently runnable example and repost to SoPW under a new subject (containing Class::Struct).

Anno