use strict;
use warnings;

my %HoH = ( a => { value1 => "foo", value2 => 1 },
            e => { value1 => "bar", value2 => 2 },
            b => { value1 => "foo", value2 => 2 },
            f => { value1 => "bar", value2 => 2 },
            d => { value1 => "foo", value2 => 3 },
            c => { value1 => "bar", value2 => 5 },
            h => { value1 => "foo", value2 => 4 },
            g => { value1 => "foo", value2 => 4 } );  

my @sorted = sort HoHsort keys %HoH;

sub HoHsort { $HoH{$b}{value2} <=> $HoH{$a}{value2}  ||  $a cmp $b }

print map "$_ =>=> { $HoH{$_}{value2} } \n", @sorted;