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

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

##</code><code>##

my %main = (   
               'main1' => {'m1sec1'=> ['A','B','C'],},
               'main2' => {'m2sec1'=> ['D','E','F'],},
               'main1-join' => {
                                'm1sec1'=> ['AX','BX','CX',
                                            'AY','BY','CY',
                                            'AZ','AY','AZ'],
                                },                          
                'main2-join' => {
                                 'm2sec1'=> ['DX','EX','FX',
                                             'DY','EY','FY',
                                             'DZ','EZ','FZ], 
                                 }
             );

##</code><code>##

use Data::Dumper;
my %nhash;

foreach  my $sd ( keys %seed )
{
    foreach  my $sdsub ( sort keys %{$seed{$sd}} )
    {

        my %temphash; 
        foreach  my $valseed ( @{$seed{$sd}{$sdsub}}  )
        {
           my $join; 

     INNER: foreach  my $mn ( keys %main )
            {
                foreach  my $msec ( sort keys %{$main{$mn}} )
                {

                    my @store;
                    foreach  my $valmain( @{$main{$mn}{$msec}}  )
                    {
                        #print $valmain.$valseed,"\n";
                        $join = $valmain.$valseed;
                        push @store,$join;
                        last INNER if (length($join) > 2);
                    }              
                    
                    $temphash{$msec} = [ @store ];
                    $main{$mn."-join"} = {%temphash};
                }           
                  
            }               
            #print "$valseed\n";
        }              

        
    }           
}               


print Dumper \%main ;