<doco> http://www.ruby-doc.org/core-2.1.0/Hash.html

Hashes allow an alternate syntax form when your keys are always symbols. 
Instead of

options = { :font_size => 10, :font_family => "Arial" }
You could write it as:

options = { font_size: 10, font_family: "Arial" }

Really ? :-) 

Let me see :-

arup@linux-wzza:~/Ruby> pry
[1] pry(main)> { :$foo => 12 }
=> {:$foo=>12}
[2] pry(main)> { $foo: 12 }
SyntaxError: unexpected ':', expecting =>
{ $foo: 12 }
       ^
[2] pry(main)>

Doco is not complete. It says use the old syntax, which is always safe.

-- 
================
Regards,
Arup Rakshit
================
Debugging is twice as hard as writing the code in the first place. Therefore, 
if you write the code as cleverly as possible, you are, by definition, not 
smart enough to debug it.

--Brian Kernighan