#!/usr/bin/Perl
# The standard header for any perl script that specifies where to find the 
# Perl interpreter used to run the following script

print <<antiTHESIS;
# Tells Perl to print (output) everything that appears from now onwards 
# until a single line containing the text "antiTHESIS"

# thesis goes here but ends with the word antiTHESIS

use Net::FTP;
# Tells Perl to load a standard library that provides support for FTPing 
# files between machines. This is often a standard part of what is known
# as the CPAN library (Comprehensive Perl Archive Network)

local $/;
# This undefines Perl's "input record separator", which means that when
# reading a file, it no longer stops at the end of a single line, but
# rather carries on until the entire fire has been read.

open       SOURCE, "<$0";
# Creates a file handle (a way to reference a file) called SOURCE
# by opening for input (<) the script's own source file ($0)

$source = <SOURCE>;
# Reads the entire file into a variable called $source. Because $/
# was undefined previously, this reads the entire file (it's called
# a "slurp" when this happens)

close      SOURCE;
# Closes the file, ie we no longer need to access the file.

$beginning = index($source, 'antiTHESIS') + 13;
# Searches through the variable $source for the first appearance
# of the string "antiTHESIS". When it has found the character position,
# it stores this in $beginning and adds 13 to it (which is the length
# of the string "antiTHESIS")

$end       = index($source, 'antiTHESIS', $beginning + 1) - 1;
# Searches through the variable $source, starting at the character
# position we just found, for the next occurance of the string 
# "antiTHESIS", storing this second character position in a 
# variable called $end, but subtracts 1 from it

$byte1     = $beginning + rand($end - $beginning);
# Picks a first random number between $beginning and $end

$byte2     = $beginning + rand($end - $beginning);
# Picks a second random number between $beginning and $end

(substr($source, $byte1, 1), substr($source, $byte2, 1)) = (substr($source, $byte2, 1), substr($source, $byte1, 1));
# Swaps the two characters in the string $source at the positions $byte1 and $byte2
# Most languages wont let you do this is one go, you have to use a third 
# temporary variable while you switch over the values. However in Perl you
# can do this by implying two temporary lists, the first one references 
# the characters (ie. substrings) at positions $byte1 and $byte2, the 
# second list contains the actual characters at positions $byte2 and $byte1
# (note the swapped order in the second list)

open  SOURCE, ">$0";
# Creates a file handle (also called SOURCE, although it's an entirely
# new handle) by opening for output (>) and thus creating a blank file
# with the name of the script's own source file ($0). This is a 
# self-destructive action, since if the script crashes between here
# and it succesfully writing the file, it will have erased it's own
# source code forever.

print SOURCE $source;
# Write the contents of the variable $source to the file handle SOURCE

close SOURCE;
# As before, closes the file handle.

if ($source !~ /disorder can lead to a sense of new order/) {
# A conditional: everything between here and the closing } will only
# execute if the variable $source *DOES NOT* contain a string that says
# "disorder can lead to a new sense of order" - this is achieved by using a
# simple regular expression (denoted by the !~ and two /slashes/)
# ...The ! represents the 'NOT' condition

  $ftp = Net::FTP->new("thesis.anti-thesis.net");
  # Create an object from the Net::FTP library that will connect to the 
  # server thesis.anti-thesis.net

  $ftp -> login("antithesis", "sisehtitna");
  # Gets the object to log into the server using a username and password

  $ftp -> cwd("Sites");
  # Gets the object to change directory to "Sites" on the remote server

  $ftp -> put($0);
  # Gets the object to upload (PUT) a file onto the FTP server. The
  # file to upload is the script's own source file ($0)

  $ftp -> quit;
  # Gets the object to close the connection and quit doing any FTP 
  # activity

}
# The end of the conditional segment