#!/usr/bin/perl

use strict;
use warnings;

my $data = '[[\'S\',[\'VMFIN\',[\'NP\',[\'PPER\']],[\'VP\',[[\'AVP\',[\'ADV\']],[\'AVP\',[\'ADV\']],[\'NP\',[\'NN\']],\'VVINF\']]]]]';
my $nr_open_brackets = $data =~ tr/\[/\[/;
my $nr_close_brackets = $data =~ tr/\]/\]/;
print "open: $nr_open_brackets, close: $nr_close_brackets";