I think the confusion stems from (x,y,z,etc) which looks like an array; when, in fact, it's a string, i.e. '(x,y,z,etc)'.

Assuming I've got that right, this piece of code shows how to split the data. I'm still not entirely sure what you mean by "There are also times when there is no data": I've added 3 additional tests with no data between commas, between parentheses and between single-quotes.

#!/usr/bin/env perl

use strict;
use warnings;

use Data::Dumper;

my $res_re = qr{ \A [(] ( .* ) [)] \z }x;

my @all_res = (
    ['(x,y,z,etc)', 'maybe other stuff'],
    ['(x,y,z,etc,,abc,,,def)', 'maybe other stuff'],
    ['()', 'maybe other stuff'],
    ['', 'maybe other stuff'],
);

for (@all_res) {
    my @res = @$_;
    print Dumper \@res;
    $res[0] = '()' unless $res[0];

    my $res_wanted = [ split /,/ => ($res[0] =~ $res_re)[0] ];
    $res_wanted = [ '' ] unless @$res_wanted;
    print Dumper $res_wanted;
    print '-' x 60, "\n";
}
[download]

Here's the output:

$ pm_split_res_for_excel.pl
$VAR1 = [
          '(x,y,z,etc)',
          'maybe other stuff'
        ];
$VAR1 = [
          'x',
          'y',
          'z',
          'etc'
        ];
------------------------------------------------------------
$VAR1 = [
          '(x,y,z,etc,,abc,,,def)',
          'maybe other stuff'
        ];
$VAR1 = [
          'x',
          'y',
          'z',
          'etc',
          '',
          'abc',
          '',
          '',
          'def'
        ];
------------------------------------------------------------
$VAR1 = [
          '()',
          'maybe other stuff'
        ];
$VAR1 = [
          ''
        ];
------------------------------------------------------------
$VAR1 = [
          '',
          'maybe other stuff'
        ];
$VAR1 = [
          ''
        ];
------------------------------------------------------------
[download]