For, schmor. MAP ALL THE THINGS!

use 5.018;
my @a = map {qq{c_${_}_mm}} 1 .. 4;
my @b = ( 1 .. 9, 0 );
my $out = join(
    qq{\n},
    map { join( q{ }, @{$_} ) }
    map { my $i = $_; [ map {qq{${_}_$i}} @a ] } @b
);

say $out;
__END__
c_1_mm_1 c_2_mm_1 c_3_mm_1 c_4_mm_1
c_1_mm_2 c_2_mm_2 c_3_mm_2 c_4_mm_2
c_1_mm_3 c_2_mm_3 c_3_mm_3 c_4_mm_3
c_1_mm_4 c_2_mm_4 c_3_mm_4 c_4_mm_4
c_1_mm_5 c_2_mm_5 c_3_mm_5 c_4_mm_5
c_1_mm_6 c_2_mm_6 c_3_mm_6 c_4_mm_6
c_1_mm_7 c_2_mm_7 c_3_mm_7 c_4_mm_7
c_1_mm_8 c_2_mm_8 c_3_mm_8 c_4_mm_8
c_1_mm_9 c_2_mm_9 c_3_mm_9 c_4_mm_9
c_1_mm_0 c_2_mm_0 c_3_mm_0 c_4_mm_0
[download]

(Alternately: Yo dawg we heard you like maps . . .)