This custom block works exactly how the 'script variables' block works, except the script variables can't be accessed outside of the area. 
Interesting that you're able to get multiple-upvar inputs. How did you get that?
But by the way, this is incredible. 
This time, it wasn't modifying the code, I made the first input the slot type '112' (100 - multiple, 12 - upvar) by using set [slots] of block. 
helpmepls
What do you mean by this?
Oh, I got it.
The 3 variables are hel, pme, and pls, which combined into helpmepls. It stands for Help me, please!.
ahhh
smart!
Oh that's really clever! So, could I make List(unevaluated) that way? Would it actually work as desired?
Are you talking about making a multiple input Any (unevaluated) input? Or like an actual thing like List (unevaluated)?
I feel like people can make it, just not purely by input.
I was expecting something more like (numbers 1 through 10)->(list[1][2][3][...][10])
In Snap! 10, in the Metaprogramming library, there's a blockify ⌸ block. That could make numbers from 1 to 10 to [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].
EDIT: I recently made a blockify block:
Import:
Nice artwork but like can you put the actual blocks in the image too for those skimming through or something
The script pic in their post is a smart script pic, so I have no clue why they bothered to put in the other custom image.
Actual List (unevaluated). My application is that I want
(whose second input is Any (unevaluated)) to look like
but still have that input be unevaluated.
I figured if you could make Upvar (variadic) by adding its two component flags, mabye you could make an input type by adding (unevaluated) to List.
I actually made this tutorial to place code in images: