Convert::Bencode_XS exists for a couple of reasons, first of all
performance. Especially bdecode() is between 10 and 200 times faster
than Convert::Bencode version (depending on file): the great speed
increase is in part due to the iterative algorithm used. bencode() is
written in C for better performance, but it still uses a recursive
algorithm. It manages to be around 3 to 5 times faster than
Convert::Bencode version. Check out the "extras" directory in this
distribution for benchmarks.

WWW: http://search.cpan.org/dist/Convert-Bencode_XS/