On #moose, the channel for a popular modern dialect of Object Oriented Perl, Debolaz asked:

 <Debolaz> Is there a simple way to produce an array of array 
           like [[1..4],[1..4]] without having to specify the 
           [1..4] multiple times?

Matt Trout's reply confused me at first

 <@mst> map { [ 1..4 ] } (1, 2)

because I thought there was a more straight-forward obvious answer:

    ([1..4]) x 2

Of course, as it happens, I was wrong… there is a problem with my
version, and it's clear if you print the structure out using Data::Dumper

 $VAR1 = [
          [ 1, 2, 3, 4 ],
          $VAR1->[0]
         ];

The same reference is cloned. This wouldn't be a problem in Haskell
of course — being a pure language, there's no way reusing the same
memory address could cause a problem. So you can just write:

  > replicate 2 [1..4]

Peregrin suggested

   (eval { [1..4] }) x2

but this also reused the array. My best solution was

use Storable qw(dclone);   
map { dclone $_ } ([1..4]) x 2

which is also quite yucky. Debolaz ended up using a variant of Matt's solution:

  map [ 1..4 ], (1,2)

I never use map EXPR, LIST style (probably I read that it could be
confusing at an impressionable age…) but that does seem fairly
legible.