#!/usr/bin/perl

use strict;
use warnings;

# NOTE: The @sourcedata array is the representation of 
# the data as if it were read from a file by:
#
#   open(FH, $sourcefilename) || die ...
#   my @sourcedata = <FH>;
#   close FH;
#
# Since the source file is huge, I need to process the
# file line by line

# NOTE: I updated this array to reflect an array of lines
my @sourcedata = (
"\n",
"1\n",
"\n",
"\n",
"b\n",
"\n",
"1\n",
"\n",
"\n",
"\n",
"\n",
"_____ 2\n",
"\n",
"\n",
"\n"
);

# The desired result of processing a small data sample:
my @desiredoutput = qq(

1

b

1
_____ 2    # NOTE: preceding newlines have been collapsed



);