use strict;
use warnings;
use Data::Dumper;
my %nhash;

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

my %seed = ( 'seed' => {'seed1'=> ['X','Y','Z']},);
my @main1 = @{$main{'main1'}{'m1sec1'}};
my @main2 = @{$main{'main2'}{'m2sec1'}};
my @seed_a = @{$seed{'seed'}{'seed1'}};
my @m1sec1;
my @m2sec1;

for my $s (@seed_a)
    {
    push @m1sec1, "$_$s" for (@main1);
    push @m2sec1, "$_$s" for (@main2);
    }

$main{'main-join1'} = {'m1sec1' => [@m1sec1]};
$main{'main-join2'} = {'m2sec1' => [@m2sec1]};

print Dumper \%main;