filename => '@',            # @ = array (of char) = string

##</code><code>##

filename => '$',

##</code><code>##

use strict;
use warnings;
use MooX::Struct Document => [ qw($fileID $filename @tags) ];

my $doc = Document[ 123, 'SampleFileName', [ qw(tag1 tag2 tag3) ] ];

printf "File ID:  %s\n", $doc->fileID;
printf "Filename: %s\n", $doc->filename;
printf "Tags:     %s\n", join(', ', @{ $doc->tags });

##</code><code>##

22:52 >perl 1068_SoPW.pl
File ID:  123
Filename: SampleFileName
Tags:     tag1, tag2, tag3

22:52 >