package Cls;
use Moose;

has an_array => (
    traits  => ['Array'],
    isa     => 'ArrayRef[Str]',
    is      => 'rw',
    # !!! forgotten default to empty array
    handles => {
        list_array => 'elements',
        add_item   => 'push',
    },
);

package main;

func();

sub func {
    my $c = Cls->new();
    $c->add_item('String');
}