Add Last Raised Exception In The Call Stack as a ruby til.

README.md

@@ -118,6 +118,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [Evaluating One-Off Commands](ruby/evaluating-one-off-commands.md)
 - [FactoryGirl Sequences](ruby/factory-girl-sequences.md)
 - [Finding The Source of Ruby Methods](ruby/finding-the-source-of-ruby-methods.md)
+- [Last Raised Exception In The Call Stack](ruby/last-raised-exception-in-the-call-stack.md)
 - [Limit Split](ruby/limit-split.md)
 - [Listing Local Variables](ruby/listing-local-variables.md)
 - [Next And Previous Floats](ruby/next-and-previous-floats.md)

ruby/last-raised-exception-in-the-call-stack.md

@@ -0,0 +1,18 @@
+# Last Raised Exception In The Call Stack
+
+In Ruby, the `$!` global variable contains the last exception that was
+raised in the current call stack. This makes it trivial to check what error
+is being rescued even if it hasn't been captured in a local variable.
+
+```ruby
+class MyError < StandardError; end
+
+def do_stuff
+  raise MyError
+rescue
+  puts "rescuing #{$!}"
+end
+
+do_stuff
+#=> rescuing MyError
+```