scripting FAQ - miura1729/mruby GitHub Wiki
> class String
* def +(s1)
* end
* end
=> nil
> "a" + "b"
=> "ab"
This causes a error in CRuby's irb, and returns nil
in CRuby.
This behavior is a limitation by the current implementation.
> alias $a $__a__
line 1: syntax error, unexpected tGVAR
Aliasing global variables using alias statement is out of ISO scope. it's mruby limitation.
See also mruby/issues#1154.