===

        # Regexp.===

(from ruby core)
---
    rxp === str   -> true or false

---

Case Equality---Used in case statements.

    a = "HELLO"
    case a
    when /\A[a-z]*\z/; print "Lower case\n"
    when /\A[A-Z]*\z/; print "Upper case\n"
    else;              print "Mixed case\n"
    end
    #=> "Upper case"

Following a regular expression literal with the #=== operator allows you
to compare against a String.

    /^[a-z]*$/ === "HELLO" #=> false
    /^[A-Z]*$/ === "HELLO" #=> true