Pangram checker

You are encouraged to solve this task according to the task description, using any language you may know.
A pangram is a sentence that contains all the letters of the English alphabet at least once.

For example:   The quick brown fox jumps over the lazy dog.



Task

Write a function or method to check a sentence to see if it is a   pangram   (or not)   and show its use.



Related tasks

   determine if a string has all the same characters
   determine if a string has all unique characters


pangram? = { sentence |
  letters = [:a :b :c :d :e :f :g :h :i :j :k :l :m
    :n :o :p :q :r :s :t :u :v :w :x :y :z]
 
    sentence.downcase!
 
    letters.reject! { l |
      sentence.include? l
    }
 
  letters.empty?
}
 
p pangram? 'The quick brown fox jumps over the lazy dog.' #Prints true
p pangram? 'Probably not a pangram.'  #Prints false