This question arises out of a couple of recent threads and may or may
not be a Ruby-specific question.

I can check with a character class if one of the characters in the
class exists or does not exist, but can I use a regexp to check if a
string absolutely contains all of the characters in the class?

Using a set perspective, I can do it like this in irb...

s1 = "hello there"
s2 = "ohi"
(s2.unpack('c*') & s1.unpack('c*')).size == s2.size

=>  false

I use unpack to avoid creating a bunch of String objects, one for each
element in the array, which would happen if I used #split.  What I'm
wondering is if there is a way to do this with a simple regexp.

Thanks,
Todd