They will all start and end a literal string.

A literal string can contain any characters except the end sequence.

The main usecase is writing code in a string.

As an example:

string test = #{
This is a literal string.
They can contain any characters, no de-quoting is done at all.

So, as an example, foo "bar" 'gazonk' \

Valid quote sequences are #{, #( and #[.
They are ended by # followed by }, ) and ], respectively.

So, you can use the two other quotes inside the string, if you want to, like:

Also, no preprocessing is done inside the string.

The main usecase for these strings is to write code in code.