#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my $data='{key1={key11=value11} | key2 = value2 | key3 = {key31=value31 | key32 = value32 | key33 = {key331=value331}}}';

sub parse($)
{
  my $data=shift(@_);
  my $rcu;
  $rcu=sub
  {
   my $ref;
   if($data=~s/^\s*\{//s)
   {
    $ref={};
    while(index($data,'}')!=0)
    {
     $data=~s/^[\|\s]*(.+?)\s*=//s;
     my $n=$1;
     $ref->{$n}=$rcu->();
    }
    $data=~s/^}//;
   }
   else
   {
    $data=~s/^\s*(.+?)\s*(\||\})/$2/s;
    $ref=$1;
   }
   return $ref;
  };
  return $rcu->();
}

print Dumper(parse($data))."\n";