#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my $string = "(a,b,(c,d,(e,f,g)))";
$string =~ s/([^,\(\)]+)/"$1"/gsm;    # quote content
$string =~ tr/\(\)/\[\]/;             # replace braces

my @LoL;                              # define list
eval("\@LoL = $test;");               # fill LoL

print Dumper @LoL;

__DATA__

Output:
$VAR1 = [
          'a',
          'b',
          [
            'c',
            'd',
            [
              'e',
              'f',
              'g'
            ]
          ]
        ];