# If I were doing this as part of a production piece, and
  # I figured it would be reused and extended and so forth,
  # I'd probably write a little sub to spit out a comma-
  # separated list of integers, and regex it into the
  # original sentence. But I don't think you need that
  # complexity.
  if (working_sentence =~ /#\d+#/) {
    # now we take an Array Slice* from the array of numbers
    # we got from file. We use $1 from the preceding regex
    # because... well, because we can.
    my @working_numbers = @numbers[0..$1-1];
    # remove that slice from the numbers array
    delete @numbers[0..$1-1];
    # join the numbers into a comma-separated list
    my $number_list = join ', ', @working_numbers;
    # and insert it into the original sentence
    $working_sentence =~ /#\d+/$number_list/;
  }