Well yacoubean, I wish I could be more help but it's 2 in the morning and all I could think of is the following, which is food for thought at best.

#!/usr/bin/perl

# hmm, try bleeping...

use strict;

my @badwords = qw(crud poop darn);

my $cleanbook;

# i wonder if it will work...
my $match = join("|",@badwords); # lazy, not checking badwords.
while (<DATA>) {
    # ahh, inefficiency!
    while ($_ =~ /$match/i) {
        my $bad = $&;
        (my $bloop = $bad) =~ s/(?<=\w)\w/\*/sg;
        $_ =~ s/$bad/$bloop/sg;
    }
    $cleanbook .= $_;
}

print $cleanbook;

__DATA__
"Crud," said Travis.  But then, Travis was
always something of a poopy-head.  He could
never keep to his darned self.  Darn it Travis!
[download]

This gives me:

[frost@louddrunk]$ perl t.pl
"C***," said Travis.  But then, Travis was
always something of a p***y-head.  He could
never keep to his d***ed self.  D*** it Travis!
[download]

...which may or may not be useful in your case. I was just thinking that if I were in your shoes I'd probably rather bl**p the profanities than replace them with gentler versions.

Erasing them requires too much skill with Grammar::Parse, and replacing them with other words is, well, putting words in people's mouths.

On the other hand, the profane among us are quite used to the occasional obfuscation...