Simply I tried this and seems to be working:-

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

my ($sorthash);
$sorthash->{'10'}->{'20'}= '1';
$sorthash->{'40'}->{'50'}= '4';
$sorthash->{'20'}->{'30'}= '2';


foreach my $diff (sort {$sorthash->{$b} <=> $sorthash->{$a}} keys %{$s
+orthash}) {
    foreach my $rptNo (keys %{$sorthash->{$diff}}) {
        print "$diff--- $rptNo\n";

    }
}
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By: Kuldip Singh Behal