Modifying string

[Ducasse]

random finding in PBE8 (probably there is a better place. post this directly to github?)
12.18 Strings
->Another important difference is that a String is mutable, whereas a Symbol is immutable.
-> 'hello' at: 2 put: $u; yourself
-> 'hullo'
Does not work anymore in Pharo 9 because in Pharo 9 you cannot modify a string literal (nor should you). But it is PBE8 and not PBE9..
stephan03/04/2021
'hello' beWritableObject;at: 2 put: $u; yourself
make it explicit
markus03/05/2021
'hello' copy at: 2 put: $u; yourself
or create a copy