How do Shopify/Liquid and shopify.dev differ?

[sebastienros]

I am often using the code blocks in https://shopify.dev/docs/api/liquid#liquid_basics to test some snippets of liquid. However it seems like the results vary with this repository. Here is an example, where last and first can be used on a string, but I can't find this logic in this repository.

Another example is identifiers, where on the shopify.dev you can use $ as the first char, but in this repository the Regex for identifiers doesn't include it.

What are the reasons for these differences? Which one is correct?