```console
% find -s lib -type f -name '*.rb' -exec ruby -cw {} \;
lib/mruby/build/command.rb:320: warning: `+' after local variable or literal is interpreted as binary operator
lib/mruby/build/command.rb:320: warning: even though it seems like unary operator
Syntax OK
Syntax OK
Syntax OK
Syntax OK
Syntax OK
lib/mruby/gem.rb:469: warning: `&' interpreted as argument prefix
Syntax OK
Syntax OK
Syntax OK
Syntax OK
```