use strict;
use lib ("./Lib");
use Datum;
my $datum = new Datum;

##</code><code>##

package Datum;

use strict;
use warnings;
use Data::Dumper;
use Class::Struct;

struct Datum => {
    heights_agl => '@',
};

sub heights_agl {
    my $self = shift;
    if (@_) {
        $self->set_values(Variable=>'heights_agl',@_);
    }
}

sub set_values {
    my $self = shift;
    my %args = @_;
    die Dumper \@_;
}

1;

##</code><code>##

C:\Tmp\debug.4>perl driver.pl
function 'heights_agl' already defined, overrides struct accessor method at Lib/Datum.pm line 8.

C:\Tmp\debug.4>perl -v

This is perl 5, version 16, subversion 3 (v5.16.3) built for MSWin32-x64-multi-thread

##</code><code>##

$ perl driver.pl
function 'heights_agl' already defined, overrides struct accessor method at Lib/Datum.pm line 8.
Odd number of elements in hash assignment at Lib/Datum.pm line 25.
$VAR1 = [
          'Variable',
          'heights_agl',
          []
        ];
$ perl -v

This is perl 5, version 26, subversion 1 (v5.26.1) built for x86_64-linux-gnu-thread-multi
(with 67 registered patches, see perl -V for more detail)