#!/usr/local/bin/perl

require 5.006;

my $braces;
$braces = qr/(\{(?:(?>[^\{\}]+)|(??{$braces}))*\})/;

sub extract_braces {
  my($str, $level) = @_;
  while ($str =~ m!$braces!g) {
    my $inside = $1;
    print "\t" x $level, $inside, "\n";
    $inside =~ s/\{(.*)\}/$1/;
    extract_braces($inside, $level + 1);
  }
}

my $str = '0a { 1a { 1.1a } 1b { 1.2a    } 1c { 1.3a { 1.3.1a } 1.3b }  } 0b { 2a { 2.1a}  } 0c';

extract_braces($str, 0);

__END__