BashForth is a ForthInterpreter, written entirely in the bash scripting language. It requires bash v3.xx or higher. Its virtual machine makes use of StringThreadedCode. Because its source code doesn't need to be compiled, it is highly portable (to any platform running bash). Previous versions can be found in the versions archive.

here is a screen shot, taken from a BashForth session:

There comes now Object-Oriented programming right to the input line of your bash prompt, through an OOPS extension for Bashforth. In the same place, some more trivial examples can be found too.