This looks like a job for Text::Balanced!

#!/usr/bin/perl
use strict; use warnings;
use Text::Balanced qw/extract_bracketed extract_multiple/;

my $test="[a,b],c,'d',[e,[f,g,h,[i,j],k,l],m,n],o,p";

my @split = grep { $_ ne ',' }
  extract_multiple( $test, [ \&extract_bracketed,
                             qr/[^\[,]+/,
                             ',',
                           ]
                  );

print "@split\n";
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Note: The default extract_bracketed will also extract (), {}, and <> delimited strings. Replace \&extract_bracketed with sub { extract_bracketed($_[0], '[]') } to restrict to [] delimited chunks.