If you look to the right of SQL it announces it's using PostgreSQL's "PL/SQL", not Oracle's (I was going crazy till I noticed).

I have no idea yet of PostgreSQL but I found this:

https://www.postgresqltutorial.com/dollar-quoted-string-constants/
Using dollar-quoted string constant in anonymous blocks

The code in the block must be surrounded by single quotes (...)
To avoid escaping every single quotes and backslashes, you can use the dollar-quoted string (...)

Same applies to our case: "Using dollar-quoted string constants in functions"