Icon and Pike are two programming languages that I probably didn't need to learn. Griswold's book on the Icon implementation was OK; it describes a complete compiler, intermediate instruction set and a VM in a compact book, but so did "A Little Smalltalk", in a far smaller frame and with class.
Icon is a "modern" SNOBOL, if you want that sort of a thing. Most Icon books and publications are online as well:
http://www.cs.arizona.edu/icon/books.htm