STklos is a free Scheme system compliant with the languages features
defined in R7RS. The aim of this implementation is to be fast as well
as light. The implementation is based on an ad-hoc Virtual Machine.

The salient points of STklos are:

an efficient and powerful object system based on CLOS providing
Multiple Inheritance,
Generic Functions,
Multi-methodsp
an efficient MOP (Meta Object Protocol)
a simple to use module system
a full tower of numbers implementation, as defined in R5RS,
easy connection to the GTK+ toolkit,
a Perl compatible regular expressions thanks to the PCRE package,
it implements properly tail recursive calls.