Seems there are a couple of ways of going about this depending on how much of the whole parsing problem this is. One way is to hand roll a recursive decent parser. Another way is to use Parse::RecDescent to generate the parser for you. If the data you have shown is representative of the worst case problem then hand rolling the parser is probably a reasonable approach. If it gets much more complex than that then using the module to generate a parser is probably a good idea.

You might like to tell us something of the larger picture in case that hints at better ways to solve the larger problem rather than the fine focus on the parsing problem. The best approach to solving the parsing issue may well depend on what you want to do with the parsed result.

Update: as an exercise I wrote the following code that may be a starting point for rolling parser:

use strict;
use warnings;
use Data::Dump::Streamer;

my $contents = <<'BLOCK';
create item "xxx" {
  remove entry "xxx"
  add entry "yy" "xxx" {
     item1=xxxx,
     item2=xxxx,
  }
  add diffenent entry "xxx" {
     item1=xxx,
     item2=xxxx,
     item3=xxx
     add subitem {
         item1=xxx,
         item2=xxx,
         item3=xxx
      }
      add subitem {
         item1=xxx,
         item2=xxx,
      }
   }
   another type {
        item1=xxx
   } with "xxx"
 }
BLOCK

my @tokens = split /\s+/, $contents;
my @chunks;

push @chunks, ExtractChunks (\@tokens);
Dump (\@chunks);


sub ExtractChunks {
    my $tokens = shift;
    my @chunks;
    
    while (@$tokens) {
        my $token = shift @$tokens;
        
        if ($token =~ /{/) {
            push @chunks, ExtractChunks ($tokens);
        } elsif ($token =~ /}/) {
            last;
        } else {
            push @chunks, $token;
        }
    }
    
    return \@chunks;
}
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Prints:

$ARRAY1 = [ [
            'create',
            'item',
            '"xxx"',
            [
              'remove',
              'entry',
              '"xxx"',
              'add',
              'entry',
              '"yy"',
              '"xxx"',
              [
                'item1=xxxx,',
                'item2=xxxx,'
              ],
              'add',
              'diffenent',
              'entry',
              '"xxx"',
              [
                'item1=xxx,',
                'item2=xxxx,',
                'item3=xxx',
                'add',
                'subitem',
                [
                  'item1=xxx,',
                  'item2=xxx,',
                  'item3=xxx'
                ],
                'add',
                'subitem',
                [
                  'item1=xxx,',
                  'item2=xxx,'
                ]
              ],
              'another',
              'type',
              [ 'item1=xxx' ],
              'with',
              '"xxx"'
            ]
          ] ];
[download]