Just another update

Task/Copy-a-string/Ruby/copy-a-string-1.rb

@@ -0,0 +1,9 @@
+original = "hello"
+reference = original          # copies reference
+copy1 = original.dup          # instance of original.class
+copy2 = String.new(original)  # instance of String
+
+original << " world!"         # append
+p reference                   #=> "hello world!"
+p copy1                       #=> "hello"
+p copy2                       #=> "hello"

Task/Copy-a-string/Ruby/copy-a-string-2.rb

@@ -0,0 +1,7 @@
+original = "hello".freeze     # prevents further modifications
+copy1 = original.dup          # copies contents (without status)
+copy2 = original.clone        # copies contents (with status)
+p copy1.frozen?               #=> false
+p copy1 << " world!"          #=> "hello world!"
+p copy2.frozen?               #=> true
+p copy2 << " world!"          #=> can't modify frozen String (RuntimeError)

Task/Copy-a-string/Ruby/copy-a-string.rb

@@ -1,4 +0,0 @@
-original = "hello"
-reference = original
-copy1 = original.dup          # instance of original.class
-copy2 = String.new(original)  # instance of String