#!/usr/bin/perl
use strict;
use warnings;
use feature "say";


my $free_space = {
  node3   => { cores => 11, mem => 200 },
  node10  => { cores => 10, mem => 900 },
  node12  => { cores => 11, mem => 500 },
  node23  => { cores => 12, mem => 350 },
  node456 => { cores => 12, mem => 400 },
  node534 => { cores => 12, mem => 400 }, 
};

say "@$_" for sort { $b->[0] <=> $a->[0] or $b->[1] <=> $a->[1] or $a->[2] cmp $b->[2] } 
       map { [$free_space->{$_}{cores}, $free_space->{$_}{mem}, $_ ]} keys %$free_space;

##</code><code>##

12 400 node456
12 400 node534
12 350 node23
11 500 node12
11 200 node3
10 900 node10