previous version of the document recommended colon ( : ) for the prefix, however, it was problematic, because Windows doesn’t allow colons in file names, so it wasn’t possible to name an autoload function this way,

the arrow has a rationale behind – it denotes the execution coming back to the function at a later time, after it has been registered as a callback or a handler,

the arrow is easy to type on most keyboard layouts – it is Right-Alt + I ; in case of problems with typing the character can be always copied – handler functions do occur in the code rarely,