Stactal

Stactal is an esolang created by User:Ϫ for the sole purpose of hurting your brain.

Fundamentals

Stactal is a stack-based esolang where stacks can go on other stacks. To create a new stack, you input this:

+1

This creates a new stack and assigns it the name 1. Stack names can only be numbers. To add a value to a stack, you type one of these:

"Hello World!":1   for strings
#12#:1             for pure numerical values
2:1                for other stacks
I:1                for user input

Then, to output a stack, you use this command, which outputs the stack's full contents, starting with the top. This does not alter the stack itself.

1 ->

If a stack is encountered during this command, it is instantly expanded into its contents. Stacks can be placed into other stacks even if it would cause an impossible setup (1 containing 2, 2 containing 1), but printing this arrangement will halt the program immediately.
The transfer command pops an item from one stack and pushes it onto another.

1 > 2

The conditional statement takes a stack and skips the next command if the top two commands are not equal.

1?

Go-to statements are made using this format:

{1}  go-to
...
[1]  label

To halt a program, simply type a $.

Programs

Truth Machine

+1
I:1
#1#:1
1?
{1}
1 ->
$
[1]
1 ->
{1}

Cat until "`"

+1
+2
+3
[1]
I:1
"`"
1?
{2}
1 > 2
2 ->
2 > 3
{1}
[2]
$