This should be using a backreference to ensure that things balance.  Though, really, this is "you used regex, now you have two problems" territory, and we should instead use [shellwords](http://ruby-doc.org/stdlib-1.9.3/libdoc/shellwords/rdoc/Shellwords.html#method-c-shellsplit) to do the parsing correctly instead.

Right now this fails: `--foo="bar'baz'"`, as does this: `--foo='bar"baz'`