main::(-:1):	my @matrix = ();
  DB<1> n
main::(-:2):	$matrix[2]->[3] = "What's goin' on?";
  DB<1> n
main::(-:3):	grep {/Huh?/}@$_ for @matrix;
  DB<1> print @matrix
ARRAY(0x8103f2c)
  DB<2> x @matrix
0  undef
1  undef
2  ARRAY(0x8103f2c)
   0  empty slot
   1  empty slot
   2  empty slot
   3  'What\'s goin\' on?'
  DB<3>