By the way, the initial release of Fexl will take a very simple form: A Universal Filter. The "fexl" executable will be nothing more than a program which maps standard input to standard output. So it's a filter. But it's universal because it is Turing-equivalent, capable of performing any conceivable function from stdin to stdout.

When Fexl runs, the first thing it does is read a Fexl function from standard input. The Fexl process then "becomes" that function, processing the tail of the input accordingly. Simple!