I have written a lot of XSL code which seems to be a pure functional language. (Can't change values once assigned, but you can do math an call functions etc.) I wonder how many other domain specific languages are functional?
I think Microsoft Excel would be the most common example.
If you do not use Macros. And spreadsheets are a cumbersome form of computation.
On the contrary, spreadsheets are a cool model of computation. They're live - you can update the value of any variable (cell) and all the other references update automatically. It's a dataflow model.