use strict;

{
    local $,="\t";
    print @{add_next_level(add_next_level([qw/1 2 3/], [qw/a b c/]),[qw/* _ +/])};
}

sub add_next_level {
    my ($basic_array_ref, $add_array_ref) = @_;
    my @result;
    for my $basic (@$basic_array_ref) {
        for my $additional (@$add_array_ref) {
            push @result, "$basic$additional";
        }
    }
    return \@result;
}