Probably just an oversight in posting, but there is a problem with this:

# build the grid
my @grid;
my @row = qw/01 02 03 04 05 06 07 08 09 10 11 12/;
for (1..$NUMBER_OF_ROWS) {
    push @grid, \@row;
}
[download]

#! perlmy @grid;
use strict;
use Data::Dumper;

use constant NUMBER_OF_ROWS => 12;

my @grid;
my @row = qw/01 02 03 04 05 06 07 08 09 10 11 12/;
for (1..NUMBER_OF_ROWS) {
    push @grid, \@row;
}

print Dumper \@grid;
__END__
$VAR1 = [
          [ '01', '02','03', '04', '05', '06', '07', '08', '09', '10',
+ '11', '12' ],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0]
        ];
[download]

I made the same mistake initially by coding

my @grid = ( [ '01' .. '12' ] ) x 12;
[download]

This is being addressed in p6 by a new operator (which I cannot remember if it is 'xx' or 'xxx', but the effect is to iterate it's left operand, not replicate it. (As far as I understand it).

It has become my "standard conversion" for where I want to type

my @grid = ( .... ) x $n;
[download]

but need new instances instead of replicated references to exchange the 'x' operator for map:

my @grid = map{ ... } 1 .. 12;
[download]

I appreciate your misgivings about the 1 .. 12, but that is (as it's position on the right-hand side tends to denote (to my brain) the lesser suboperation of the significant operation; namely that I am initialising the array grid with separate instances of some constant expression. (Oh. And there are 12 of them :).

Beyond the thinko, the problem I have with the for/push method is that the main objective--that of initialising the array @grid--gets lost in the noise of the construction.