Dear ikegami,
Thanks so much for your reply. I have further question, I hope you wont' mind.

Suppose I want to:
1. Add the resulting appended hash into "%seed"
2. And then use that new appended hash in %seed recursively again, keep appending it.
3. It stops until the length of the appended string is 3 (later can be any other length).

I tried to modify your first example, but I'm still stuck.

The problem with my code below mainly because the %seed has doesn't get updated, only the array that grows. What we intend is to have accumulated %seed with uniformed length in the array element (length of the element is extended longer than the initial seed).

How should I go about it? I am so sorry for troubling you so much. Really hope you don't mind to look at it. 
#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my %main = ( 'main1' => {'m1sec1'=> ['A','B','C'],},
             'main2' => {'m2sec1'=> ['D','E','F']}
     );

my %seed = ( 'seed' => {'seed1'=> ['X','Y','Z']},);


my @sd = keys(%seed);

OUTER: foreach  my $sd ( @sd )
{
    foreach  my $sdsub ( sort keys %{$seed{$sd}} )
    {
        foreach  my $valseed ( @{$seed{$sd}{$sdsub}}  )
        {
            #--
            foreach  my $mn ( keys %main )
            {
                foreach  my $msec ( sort keys %{$main{$mn}} )
                {
                    # Create hash if it doesn't exist.
                    $seed{$mn."-join"} ||= {};
                    
                    # Create array if it doesn't exist.
                    $seed{$mn."-join"}{$sdsub} ||= [];
                    
                    my $store = $seed{$mn."-join"}{$sdsub};
                   
                    # I want to push the new hash in the %seed key set
                    # (updating them)
                    # So that later it can be called again recursively
                    
                    my $tmpstr = $mn."-join";
                    push @sd, $tmpstr;

                    foreach  my $valmain( @{$main{$mn}{$msec}}  )
                    {
                      push @$store, $valmain.$valseed;
                      last OUTER if (length($valmain.$valseed) == 4);

                      # length equal 4 here so that we can
                      # capture str with length 3 (?)
                    }
               
                }
            }
        }
    }
}

print scalar(keys %seed),"\n";
print Dumper \%seed;

[download]


---
neversaint and everlastingly indebted.......

In reply to Re^2: Accumulating a Hash from Pairwise Comparison by neversaint
in thread Accumulating a Hash from Pairwise Comparison by neversaint

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