Understanding the differences
The Text object offers three different types of iterators functioning ever so slightly from each other.
The forEach method will loop over the fragments, but you cannot modify them. This is meant purely as a convenient way to loop over the expressions and read relevant information about them.
The map will replace the expression and parse the output. This means that you have to use the set method to define an output for the ExpressionFragment. You can also return a TextFragment to replace it.
The rebase method works very similar to map but instead of replacing expressions with the output, it will replace with the foundation method of the fragment. For TextFragment this behaves the normal way, but for ExpressionFragment it will insert the signature of the expression, instead of the result/output. This allows you to replace expressions before they're parsed.