In pure Perl, you don't need encryption at all if you don't really need to keep the data hidden. A simple hash data type will suffice:

my %data;
while(my $msg = get_msg()) {
    $data{$msg} = 1;
}
[download]

If you need to save this to a file or a database or whatever, you can use the Digest::MD5 or Digest::SHA1. Note: MD5 is possibly on the verge of collapse as far as security is concerned, so stay away from it if you need it for security reasons. MD5 is fine if you just need the hash properties, and it will be faster than SHA1.

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Reinvent a rounder wheel.

Note: All code is untested, unless otherwise stated