Dear Happy.Barney I tested your perl source code,You have splited the scalar value based on the open and close bracket.So it is failing one of the test case.I gave following input/output.

#!/usr/bin/perl
use strict;
use warnings;
my $test="[a[a]]";
my @stack = [];
for (split /([\[\],])/, $test) {
    next
    unless length $_;

    next
    if $_ eq ',';

    push @stack, [] and next
    if $_ eq '[';

    push @{ $stack[-2] }, pop @stack and next
    if $_ eq ']';

    push @{ $stack[-1] }, $_;
}
my $retval = $stack[0];
use Data::Dumper;
print Dumper($retval);


$VAR1 = [
          [
            'a',
            [
              'a'
            ]
          ]
        ]; 

The output should be as following.
$VAR1 = [
          [
            'a[a]'
          ]
        ];
[download]

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