#!/usr/bin/perl
my $Gibberish=<<EOGibberish;
This is a sentence.  It's not a particularly great sentence, but
it's a sentence nonetheless.  It would suck if someone accidentally
changed it!
EOGibberish

use strict;
use warnings;
use autodie;

my $search;

open my $FH, '<', $0;
binmode $FH;
seek $FH, 55, 0;
read $FH, $search, 8;
close $FH;

$Gibberish =~ s/$search/XXXXXXXX/g;

print $Gibberish;