Count words.

"no ruby, no life!"
# => {"no"=>2,"ruby"=>1,"life"=>1}

str = "no ruby, no life!"

# A.1
str.scan(/\w+/).each_with_object(Hash.new(0)){|e,h| h[e]+=1}
# => {"no"=>2, "ruby"=>1, "life"=>1}

# A.2
# 意味ないけどこんなこともできるよね。
h = Hash.new {|hash, key| hash[key.uniq] = key.size }
str.scan(/\w+/).group_by{|s|s}.values.each{|e| h[e]}
# h
# => {["no"]=>2, ["ruby"]=>1, ["life"]=>1}