$ ruby -e 'puts RUBY_VERSION' -e 'puts RUBY_ENGINE' -e 'puts -1 / 2'
3.1.1
ruby
-1

$ ./bin/mruby -e 'puts RUBY_VERSION' -e 'puts RUBY_ENGINE' -e 'puts -1 / 2'
-e:3:7: warning: ambiguous first argument; put parentheses or even spaces
3.1
mruby
0

$ git show
commit 6f2efebbb9e0d43ca471d89ea76f396baa43eb62 (HEAD, tag: 3.1.0-rc, origin/stable)
Merge: f29924c83 7e7f1b2f1
Author: mimaki <hiroshi.mimaki@gmail.com>
Date:   Mon Jan 17 21:36:52 2022 +0900
    Merge commit '7e7f1b2' into stable

$ ./bin/mruby -e 'puts RUBY_VERSION' -e 'puts RUBY_ENGINE' -e 'puts -1 / 2'
-e:3:7: warning: ambiguous first argument; put parentheses or even spaces
3.0
mruby
-1

$ git show
commit 0f45836b5954accf508f333f932741b925214471 (HEAD, tag: 3.0.0)
Author: mimaki <hiroshi.mimaki@gmail.com>
Date:   Fri Mar 5 17:07:35 2021 +0900
    Update version and release date. (mruby 3.0.0 (2021-03-05))