#!/usr/bin/perl

use strict;
use warnings;

open my $fh, 'unbase64.txt'
  or die $!;

my (@ebx, @ecx);

while ( my $ch = getc $fh ) {
  push @ebx,$ch;
  push @ecx,$ch;
}

splice @ebx, 0, 5;
splice @ecx, 0, 5;

splice @ebx, 0, 0x1e;

my @plain_text;

while ( my $ebx_ch = shift @ebx) {
  my $ecx_ch = shift @ecx;
  push @plain_text,( $ebx_ch ^ $ecx_ch );
}

printf "%s\n", join( '',@plain_text);