OK, my prototype wasn't totally correct.

Here an implementation allowing to combine multiple cross(), like in the OP 

use strict;
use warnings;
use Data::Dump qw/pp dd/;
use 5.12.0;

# https://perlmonks.org/?node_id=11121968

sub cross(&\@@) {
    my ( $code, $a_a, @b ) = @_;

    #warn pp $code, $a_a,\@b;

    map {
        $a = $_;
        map { $b=$_; &$code } @b;
    } @$a_a;
}


my @a = 1..3;
my @b = 4..6;
my @c = 7..9;


pp
  cross { $a.$b } @a,
  cross { $a.$b } @b,@c;

[download]

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[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

In reply to Re^4: nested maps by LanX
in thread nested maps by jczeus

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