Here's another way to approach the problem. I'm not sure it's a better way than holli layed out for you but if you've got a bunch of words to replace I'd think a hash might be the way to go. Unfortunately this doesn't save your puncuation, and tonight I'm at a loss on how to split and save puncuation.

With that said, here's my attempt:

#!/usr/bin/perl
use strict;
use warnings;
my ($line, $cleanbook);

my %badwords = (crud => "darn", shit => "shoot");

while ($line = <DATA>) {
    $line =~ s/["'.,!?:;\-()[\]{}|\\\/]/ /g; #replace all punctuation 
+with a space
    my @sentence = split(/\W+/,$line);
    @sentence = map {$badwords{lc($_)}?$badwords{lc($_)}:$_} @sentence
+;
    $cleanbook .=  join(' ', @sentence)."\n";
}

print $cleanbook;

__DATA__
"Crud," said Travis
"Shit, this crud is shit!"
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