What you've said kinda got me thinking about a script i saw once in my early days of programming. I had a bit of a hack and came up with this. Its pretty rough, and is only really proof of concept quality code.

The process is:

1. create your perl script
2. encrypt it
3. stick it into a header

The script

print "Hello World!\n";
print "This is an example of encrypting a perl\n";
print " script and not having the source directly viewable\n";
[download]

The encryption "engine":

#!/usr/bin/perl -w

use strict;
use Crypt::CBC;
use Data::Dumper;

local*FH;
open(FH, 'hello.pl');
my $plaintext;

while (<FH>) {
    $plaintext .= $_;
}
close FH;

my $cipher = new Crypt::CBC('hey jude!');
my $ciphertext = $cipher->encrypt_hex($plaintext);

for (my$i=0;$i<length($ciphertext);$i++) {
    print "\n" if ($i%30 == 0);
    print substr($ciphertext, $i,1);
}
[download]

And now the header:

#!/usr/bin/perl -w

use strict;
use Crypt::CBC;
use Data::Dumper;

my $ciphertext;
while (<DATA>) {
    chomp;
    $ciphertext .= $_;
}

my $cipher = new Crypt::CBC('hey jude!');
my $plaintext = $cipher->decrypt_hex($ciphertext);

print "Plaintext\n";
print "---------\n";
print "$plaintext\n\n";

print "Eval:\n";
print "-----\n";
eval $plaintext;

__DATA__
52616e646f6d4956b1de8bd854dc4f
7137bd168ab1271410ce41442407f1
aa99ff61f79b89ba7ecfca35f283f7
cd5623b70aca91aedaef5a6bb1a7f5
343e40d1973d41720dab8105623d86
d0ed903db80073d57f8148ad799647
b947ae386b327dc61488d6e16392c6
9d623d1ac1f7fd0c767f182225ce6b
66a05c247903a2321e8a737bb3da4a
fb5cf611dacbed89347997ab2db220
b1df993e95e7e0729405d84261bad4
[download]

The result:

[coolness@ryszard encrypt]# ./header.pl 
Plaintext
---------
print "Hello World!\n";
print "This is an example of encrypting a perl\n";
print " script and not having the source directly viewable\n"

Eval:
-----
Hello World!
This is an example of encrypting a perl
 script and not having the source directly viewable
[download]

Out of interest i ran it thru deparse and found:

[coolness@ryszard encrypt]# perl -MO=Deparse header.pl 
BEGIN { $^W = 1; }
use Crypt::CBC;
use Data::Dumper;
use strict 'refs';
my $ciphertext;
while (defined($_ = <DATA>)) {
    chomp $_;
    $ciphertext .= $_;
}
my $cipher = 'Crypt::CBC'->new('hey jude!');
my $plaintext = $cipher->decrypt_hex($ciphertext);
print "Plaintext\n";
print "---------\n";
print "$plaintext\n\n";
print "Eval:\n";
print "-----\n";
eval $plaintext;
__DATA__
52616e646f6d4956b1de8bd854dc4f
7137bd168ab1271410ce41442407f1
aa99ff61f79b89ba7ecfca35f283f7
cd5623b70aca91aedaef5a6bb1a7f5
343e40d1973d41720dab8105623d86
d0ed903db80073d57f8148ad799647
b947ae386b327dc61488d6e16392c6
9d623d1ac1f7fd0c767f182225ce6b
66a05c247903a2321e8a737bb3da4a
fb5cf611dacbed89347997ab2db220
b1df993e95e7e0729405d84261bad4
header.pl syntax OK
[download]

One thing i noticed while developing the above code was the last few characters of the source perl script seem to be gobbled up, resulting in the eval failing.. unfort, i dont have the time right now to fix it...

HTH

Update: and then there is always Filter::CBC - props to beatnik