There are two different implementations of Blowfish in CPAN. As I said "the CPAN implementations of Blowfish and Rijndael I am using have binary elements" (note my wording). I know that there are Pure Perl implementations of Blowfish, and obviously you are using one of them. That was not the point of my question to you.

From your posting (and your follow-up) you seem to be under the impression that using non-PurPerl modules requires forking or external process calls. Whereas I am using the faster XS implementation of Blowfish (which links against a dll) this also allows me to run the encryption code inline with my existing Perl.

The benefit of Pure Perl modules comes at installation time (when you don't need a compiler), at run time I think the interface for the two implementations of Crypt::Blowfish are exactly the same. The XS version has the same interface and is faster so, as far as I can see the selection of a Pure Perl solution only makes sense in relation to your, as you put it OS of choice.

So far the performance of my solution has turned out to be "good enough" (that is there are plenty of other places in the code that need attention before I will worry about it)