mruby/mruby — pull request #1616 by h2so5 (2013-12-23 15:17:46+00:00)
Title: verify the argument of String#=~

This code makes an infinite recursion.
```
bin/mruby -e " '' =~ '' "
trace:
[0] -e:1
-e:1: stack level too deep. (limit=(0x40000 - 128)) (RuntimeError)
```