What is "simple"?

use strict;
use warnings;

my @a = ( 1,2,3 );
my @b = ( 4,5 );
my @c = ( 6,7 );

my ( $x, $y, $z );
my @total = map { $x = $_;  map { $y = $_; map { join '', $x, $y, $_ }
+ @c } @b } @a;

{
    local $, = local $\ = $/;
    print @total;
}

__END__
[download]

Result:

146
147
156
157
246
247
256
257
346
347
356
357
[download]