#!/usr/bin/perl
use strict;
use warnings;

my %sorthash = ();

$sorthash{'10'}{'20'}= '1';
$sorthash{'40'}{'50'}= '4';
$sorthash{'20'}{'30'}= '2';

# Invert the hash
my %reverse_hash = ();
for my $keys1 (keys %sorthash ) {
    my $child_hashref = $sorthash{$keys1};
    for my $keys2 (keys %$child_hashref ) {
        $reverse_hash{$keys2}{$keys1} = $child_hashref->{$keys2};
    }
}
# Print after sorting keys
for my $keys2 (sort {$a <=> $b} keys %reverse_hash) {
    my $child_hashref = $reverse_hash{$keys2};
    for my $keys1 (sort {$a <=> $b} keys %$child_hashref) {
        print "keys: $keys1\t$keys2\t";
        print "values: $child_hashref->{$keys1}\n";
    }
}