Forth is brilliant, but my favourite concatenative language is PostScript. Most view PostScript as nothing more than a dated binary format for vector graphics. However, writing plots and diagrams in pure PS is incredibly flexible and pretty easy once you build up or find enough libraries to do what you want. Postscriptbarcode[0] is an example of a good library. [1] is a good guide to writing PS by hand.
What is PS does lack, however, is a modern debugger (or interpreter with decent error reporting) and package management.
What is PS does lack, however, is a modern debugger (or interpreter with decent error reporting) and package management.
[0] http://code.google.com/p/postscriptbarcode/ [1] http://www.math.ubc.ca/~cass/graphics/manual/