...
The pico engine also allows us to add a file extension after the function name (but before arguments in a query string) to indicate how we want the user agent to interpret a string response. Shown here are, from top to bottom, with no extension, we see the string, but with a .html extension, the browser interprets that string as a selection box widget, and with a .txt extension, shows it as plain text.
...
This is also a one-liner, but quite involved. It appends the separator, a position octet for the index of the digit within the string of digits we wish to render, and finally the actual octets for the glyph of that digit. Since this function is used as the argument to a map operator, it will be passed first the index value and then the value the index of each digit.
The pos function and a couple of missing pieces are shown here.
...