Unix dc(1) desk calculator

        One that I didn't see listed was one for the Unix dc(1) desk
calculator. That would be something like:

        [Hello, world!] p

(Strings are enclosed in brackets, and the 'p' commands prints the top of
the stack, with a newline.)

        A looping version of this program would have the command stored
in a macro that calls itself:

        [ [Hello, world!] p la x ] sa
        la x

where "sa" says to store the string on the stack as macro "a", "la" means
load macro "a" onto the stack, and "x" means execute the string on the
stack.

Unix dc(1) desk calculator (looping without stack overflow)

Here is a correction for the dc(1) variant of "Hello World". The
current one doesn't clear the stack after printing the text.
This will cause a stack overflow or nesting depth. This one
WILL be infinite!

[[Hello World!]pclxx]sxlxx