use strict;
use warnings;
use Data::Dumper;

my @broken_up;
my @array = qw( 1 2 3 # 4 5 # 6 7 8 9 # 10);
my $position = 0;
$broken_up[0] = [];
foreach my $item (@array) {
  if ($item eq '#') {
    $position++;
    $broken_up[$position] = [];
  }
  else {
    push @{ $broken_up[$position] }, $item;
  }
}

print Dumper(\@broken_up);