You could use Objects instead of plain hashes. A few weeks ago i wrote an example for someone with a similar problem. It uses Moose for OO, and you can see how it simplifies the stringification of a nested structure:

#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

package SingleState;
use Moose;

has 'state'     => (isa => 'Value', is => 'rw');
has 'value'     => (isa => 'Value', is => 'rw');
has 'position'     => (is => 'rw');

sub to_s {
    my $self = shift;
    return $self->state . "\t=>\t" . $self->value . "\n";
}

package Stat;
use Moose;

has 'states'     => (isa => 'ArrayRef', is => 'rw');
has 'title'     => (is  => 'rw');
has 'position'     => (is  => 'rw');

sub add_state {
    my $self = shift;
    return unless @_;
    push @{$self->{states}}, $_ for @_;
}

sub to_s {
    my $self = shift;
    my $o = $self->title ? "== " . $self->title . " ==\n" : '';
    $o .= $_->to_s for (sort { $a->position <=> $b->position } @{$self
+->states});
    return $o;
}

package StatSet;
use Moose;
use Data::Dumper;

has 'stats'     => (isa => 'ArrayRef', is => 'rw');

sub add_stat {
    my $self = shift;
    return unless @_;
    push @{$self->{stats}}, $_ for @_;
}

sub report {
    my $self = shift;
    my $s;
    $s .= $_->to_s . "\n" for (sort { $a->position <=> $b->position } 
+@{$self->stats});
    return  $s;
}

package main;

my $set = new StatSet;

my $stat1 = new Stat ( title => 'CPU' );
my $stat2 = new Stat ( title => 'Memory' );

my $state1 = new SingleState( state => 'Idle', value => '92', position
+ => 1 );
my $state2 = new SingleState( state => 'User', value => '0',  position
+ => 2 );
my $state3 = new SingleState( state => 'Cached', value => '531976', po
+sition => 1 );


$stat1->add_state( $state1, $state2 );
$stat1->position(1);

$stat2->add_state( $state3 );
$stat2->position(2);

$set->add_stat($stat1);
$set->add_stat($stat2);

print $set->report;
[download]

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